Journal of Clinical Immunology, Vol. 8, No. I, 1988

Immediate Effects of Intravenous IgG Administration on Peripheral Blood B and T Cells and Polymorphonuclear Cells in Patients with Myasthenia Gravis

LINDA COOK, 1 JAMES F. HOWARD, JR., 2'3 and JAMES D. FOLDS j

Accepted: August 31, 1987

Five patients with myasthenia gravis, who received treat- ment with intravenous 7S ~-globulin were monitored for changes in immunological status. Serum immunoglobutin G increased from an average of 1.4 to 4.7 g/dl during the 5-day course of therapy. Specific antibody to the acetyl- choline receptor present in three of five patients did not change. A transient decrease in total peripheral blood leukocytes was observed in five patients due to decreases in the absolute number of polymorphonuclear cells and lymphocytes in the circulation. Lymphocyte surface marker studies revealed that the percentage of surface immunoglobulin positive cells increased in all patients from an average of 13 to 26% by day 5 of therapy; however, the percentage of HLA-Dr- and Leu 12 (CD19)- positive B cells did not change. Lymphoid cells positive for the Leu 11 (CDi6) marker doubled from an average of 11 to 24% during the 5-day course of therapy. Surface Ig-positive cells and Leu 11 (CD16)-positive cells re- turned to pretreatment values by 7 days posttherapy. Helper/suppressor cell ratios slowly decreased in all patients from an average of 2.9 to 2.2 by 1 week postther- apy and remained low for several weeks. KEY WORDS: Intravenous ~-giobulin; myasthenia gravis; lym- phocyte surface markers; lymphocytes.

INTRODUCTION

High-dose human intravenous ~-globulin (IV !gG) has been used in the treatment of patients with a

~Clinical Microbiology and Immunology Laboratory, The North Carolina Memorial Hospital, Chapel Hill, North Carolina 27514.

ZDepartment of Neurology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27514.

3To whom correspondence should be addressed at Department of Neurology, 751 Clinical Sciences Building, 229H, UNC-CH, Chapel Hill, North Carolina 27514.

variety of disorders: idiopathic thrombocytopenic purpura (iTP) (1-3), platelet-alloimmunized transfu- sion recipients (4), immune neutropenia (5, 6), aplastic anemia (7), hemophilia due to anti-Factor VIII antibodies (8-12), Kawasaki's disease (13), systemic lupus erythematosus (14), bullous pemphi- goid (l 5), Felty's syndrome (16), inflammatory poly- neuropathy (17), and myasthenia gravis (MG) (18-21). No clinical improvement was seen in the platelet-alloimmunized transfusion recipients or the Felty's syndrome patients but improvement was seen in at least some of the patients with each of the other conditions.

The mechanism of action of IV IgG in patients with ITP is thought to be Fc receptor blockade of macrophages within the reticuloendothelial system by normal IgG (22). The mechanism of action of this preparation in hemophilia anti-Factor VIII disease may be the action of antiidiotype antibodies present in the IV IgG preparation against anti-Factor VIH:C antibodies present in the serum of these patients (10). Because there may be multiple mechanisms leading to the clinical improvement seen with IV IgG therapy in different diseases, a careful study of the white blood cells and immunologically related proteins in the circulation may reveal changes that occur during therapy which will lead to a better understanding of the mechanisms of action of IV IgG for each disease. In an effort to understand the mechanism Of improvement in myasthenia gravis, we have studied the levels of immunologically re- lated proteins and the numbers and types of circu- lating white blood cells from five patients with myasthenia gravis who were treated with high-dose IV IgG.

23 027t-9142/88/0100-0023506.00/0 © 1988 Plenum Publishing Corporation

24 COOK, HOWARD, AND FOLDS

M E T H O D S

Patient Selection and Treatment Protocol

All patients were diagnosed as having MG on the basis of clinical history, physical examination, and response to cholinesterase inhibitors. Pooled hu- man 7S ~/-globulin (Sandoglobulin) was adminis- tered daily for 5 days in doses of 0.4 g/kg/day by slow tV infusion as recommended by the manufac- turer. Blood samples were drawn prior to the initi- ation of therapy, daily during therapy, 24 hr follow- ing the cessation of therapy, and periodically there- after during follow-up clinic visits.

The clinical response of each patient was deter- mined by manual muscle testing performed by a single examiner on a daily basis during therapy and at each follow-up clinic visit and by electrophysi- ologic changes of neuromuscular transmission as measured by single fiber electromyography (23). Response to therapy was graded on a relative scale ranging from - I to +3: -1 , worse; 0, no change; +1, slight improvement; +2, marked improvement; and +3, complete remission.

White blood cell counts and differentials were determined daily during therapy with a Technicon H-6000 automated cell counter. When necessary, blood smears were reviewed for abnormalities by a hematopathologist. Serum IgG, IgM, and IgA levels were measured daily with a Beckman ICS rate nephlometer. Specific antibody to the acetylcholine receptor was determined by immunoprecipitation assay with radiolabeled a-bungarotoxin (24). Com- plement levels were periodically measured in two ways: C3 and C4 quantitations were done with a Beckman ICS rate nephlometer and tube CHs0 functional assays were also performed (25). From two of the patients, serum levels of immune com- plexes were measured by the Clq binding assay (Cordis Laboratories, Miami, FL).

Lymphocytes from peripheral blood samples were obtained prior to therapy, on day 3 or 4 of therapy, 24 hr following completion of therapy, 1 week posttherapy, and periodically thereafter at follow-up clinic visits. Blood was drawn into so- dium heparin Vaccutainer tubes and then layered over lymphocyte separation medium (LSM; Or- ganon Teknika Corp, Irvine, TX) to isoiate the mononuclear cells. Mononuclear cell populations were stained with monoclonal antibodies (Becton- Dickinson, Mountain View, CA) specific for lym- phocyte surface antigens or with anti-immunoglob-

ulin antisera or were used to perform sheep red cell E-rosette test assays. Determination of the percent- age of cells stained by the antibodies was done with a Becton-Dickinson FACS analyzer. Absolute numbers of lymphocyte subsets were calculated by multiplying the absolute number of lymphocytes measured by the H-6000 cell counter by the per- centage of lymphocytes positive with either the Leu 3 or the Leu 2 monoclonal antibodies.

R E S U L T S

Clinical Course

A summary of the observed clinical response for five patients following their initial course of infusion is shown in Fig. 1. All patients had some improve- ment following their infusion but the degree of improvement varied with the patient. None of the patients achieved complete remission. Clinical im- provement began as early as the fourth infusion and during the first week following therapy for most patients. Improvement lasted less than 2 months in four of seven courses of treatment. Two of the patients received a second course of therapy be- cause of a lack of significant clinical improvement 56 and 84 days following their first course of treat- ment. One had a significant relapse within a week of her second course of infusion and was removed from the study protocol; the other showed further improvement following her second course of ~- globulin therapy, but several months thereafter her strength worsened.

Effects on Circulating White Blood Cells (WBC)

A small decrease in WBC numbers was seen during five of the seven courses of therapy (Table I). In four of the courses the samples drawn on days 4 and 5 showed the most significant decrease in WBC. WBC counts returned to baseline values by 1 week posttherapy. One patient showed a decrease in WBC only in the sample drawn at one week posttreatment. When absolute numbers of polymor- phonuclear cells (PMNs), lymphocytes, mono- cytes, eosinophils, and basophils were determined, the decrease in WBC could be accounted for by a decrease in the numbers of PMNs and lympho- cytes. Absolute numbers of monocytes, eosino- phils, and basophils did not change during therapy. In a single patient, PMNs isolated from the 24-hr postinfusion blood sample were functionally normal

Journal of Clinical lmmunology, Vol. 8, No.I, 1988

EFFECTS OF IgG ON BLOOD CELLS IN MYASTHENIA GRAVIS 25

3 "

4 . . / "x / , , / '\

/ / \ \ ua i / \

Oa. / //\\ \ \

f t ,, \

0 -- I ~i I t \\ "-. .....

o !i / / - . . . . . . . . -~-__

\

\ \

\ \

0 10 2 0 3 0 4 0 5 0 6 0 7 0 8 0 D A Y S

Fig. 1. The clinical course of five patients during and following their initial course of intravenous 3,-globulin. Arrow represent ~/-globulin infusions. Clinica ! response: - 1 =worse ; 0=basel ine; 1 =improved; 2=marked improvement; 3=remission. The asterisks represent the point at Which a second course of ~/-globu!in was administered. Each symbol and line characteristic represents an individual patient and remains constant for each patient in every figure. Patient 1, &; patient 2, [3; patient 3, + ; patient 4, o; patient 5, x.

in their ability to phagocytize and mount a respira- tory burst in response to stimulus with phorbol myristic acid (PMA) and did not have detectable immunogtobulin on their surface membranes (data not shown).

Changes in Immunoglobutin and Complement Levels

As expected, IgG levels rose approximately three- fold during therapy, reaching a peak at 24 hr post- therapy, and then slowly declined over the next few weeks to baseline values (Fig. 2). In the two pa- tients with measurable antiacetylcholine receptor antibody, the quantity of antibody did not change significantly during the first 3 weeks following ther- apy in four courses of treatment. Quantitations of !GM and IGA were not significantly changed by the ~/-globulin infusions. C3, C4, and CHs0 assays did not show changes in complement component levels during or following therapy. No elevation in the levels of immune complexes as measured by the Clq binding assays were seen in the two patients in which levels were determined.

Changes in Lymphocyte Subpopulations

The percentage of cells staining with the mono- clonal antibodies recognizing surface antigens on B cells and monocytes, HLA-Dr, Leu 12 (CD19), and Leu M3, did not change during or following ther- apy.

Two alterations in lymphocyte surface markers were seen in the mononuclear cells during -/-globu- lin therapy. Percentages of mononuclear cells stained with antiimmunog!obulin rose from an av- erage of 13% (normal range, 6-15%) prior to the start of the infusions to an average of 26% in the samples drawn 24 hr after the fifth infusion (Fig. 3). This increase in surface Ig positive cells was seen in six of the seven courses of therapy and was not due to an increase in B cells with surface immunoglob- ulin since the percentage of cells stained with Leu 12 (CDI9) and HLA-Dr did not change. When anti-heavy chain-specific antiserum was used with the cells from a single patient, IgM was the surface immunoglobulin present on the majority of the cells of the initial samples. In the 24-hr postinfusion samples, about half of the lymphocytes had IgG on their surface, while the remaining cells were posi-

Journal o f Clinical Immunology, Vol. 8, No, l , 1988

26 COOK, HOWARD, AND FOLDS

Table I. Changes in Peripheral White Cell Counts ~

Day Day Day Day Day Day Day Patient 1 2 3 4 5 6 12

Total WBC count*

1 4.1 3.6 2.8 2.6 2.5 3.1 5.2 2a 8.3 3.3 3.9 4.3 2b 5.4 5.2 4.7 5.7 5.0 6.6 3.7 3 15.9 9.7 8.0 9.8 6.6 9.5 16:8 4a 5.0 4.3 5.3 4.8 5.2 6.3 6.5 4b 5.7 4.9 4.7 4.2 4.5 7.5 6.2 5 5.1 4.6 4.3 4.0 3.8 5.2 4.9

Absolute neutrophil count**

1 2.0 1.3 1.2 1.0 1.4 2.4 2a 4.5 1.4 1.7 1.5

1.9 2.5 2.1 2.5 2.5 3.6 1.5 3 11.9 6.1 5.1 6,9 3.6 6.1 11,9

2.4 2.0 2.5 2.4 2.8 3.5 3.7 2.4 2.2 1.9 2.0 6.2 3.0

5 3.4 2.9 2.9 2.7 2.6 3.3 3.2

Absolute lymphocyte count***

1 1.5 0.9 0.8 1.0 1.1 2.2 2a 2.7 1.1 1.5 2.2 2b 2.6 2.0 1.9 2.1 1.7 2.1 2.0 3 2.7 2.6 2.1 2.1 2.2 2.3 3.3 4a 2.1 1.9 2.3 1.9 1.8 2.0 2.6

2.7 2.2 2.3 2.0 0.9 4.5 5 1.1 1.1 1.0 0.8 0.7 1.2 1.2

Absolute monocyte count****

1 0.2 0.3 0.3 0.3 0.3 0.3 2a 0.9 0.5 0.4 0.3 2b 0.5 0.5 0.4 0.7 0.6 0.8 0.1 3 1.0 0.8 0.6 0.7 0.6 0.8 1.0 4a 0.2 0.3 0.3 0.3 0.4 0.6 0.1 4b 0.3 0.3 0.2 0.3 0.4 0.3 5 0.4 0.4 0.3 0.4 0.3 0.6 0.4

aAll values are expressed as K/mm 3. *Significant differences (P = 0.03) for differences between days.

**Not significant (P > 0.17) for differences between days. ***Significant differences (P = 0.0009) for differences between

days. ****Not significant (P > 0.19) for differences between days.

tive for IgM. The percentage of cells positive with the antiimmunoglobulin antisera returned to base- line values in the l-week postinfusion samples.

A second alteration in lymphocyte subpopula- tions which occurred was seen in the percentage of cells stained with the Leu 11 (CD16) monoclonal antibody, an antibody which reacts with the glyco- protein that functions as the IgG F c receptor on natural killer cells (26). The percentage of mononu- clear cells positive for the Leu 11 (CD ! 6) monoclo- nal rose from an average of 11% in the preinfusion samples to an average o.f 24% in the 24-hr postinfu- sion samples (Fig. 4). The percentage of cells pos-

itive with the Leu 11 (CD16) antibody returned to baseline levels for all but one of the patients by the 1-week posttherapy sample. The percentage ofmono- nuclear cells positive with the Leu 7 monoclonal antibody, an additional antibody which reacts with a subset of NK cells, was less than 5% in all pretherapy samples (normal range, 4-9%). No change in the percentages of these cells staining with Leu 7 Was observed during or after therapy. The percentage of T cells, as measured by sheep red cell rosette formation and surface staining with monoclonal Leu 4 (CD3), did not change signifi- cantly during or following therapy.

T cell helper/suppressor (H/S) subset ratios were also altered by the ~/-globulin infusions but this change had a muc h different time course than the changes observed in surface immunoglobulin- and Leu 11 (CD16)-Positive cells. An initial observation was made that a significant increase in a subpopula- tion of weakly Leu 2 (CD8)-positive cells could be seen in the samples with high serum IgG levels on days 3, 4, and 6. When the mononuclear cells were stained with phycoerythrin-labeled Leu 2 (CD8), a small but significant population (5-8%) of weakly stained cells were detectable. No weakly stained cells could be seen when the cells were stained with the FITC-labeled Leu 2 (CD8). H/S ratios were therefore calculated with the percentages of cells stained with the phycoerythrin-labeled Leu 2 (CDS).

Helper/suppressor ratios calculated for the pre- treatment samples from the initial course of therapy averaged 2.9, at the top of our established normal range of 1.5 to 3.1 (Fig. 5, Table II). The H/S ratio decreased slightly in all patients during the therapy, to an overall average of 2.2 by the 24-hr postinfu- sion samples. Lymphocyte subset ratios remained lower than their baseline or continued to dec/ease during the next month to an average of 1.9 for three of the courses of therapy. In contrast, H/S ratios in three of the courses returned to near baseline values by the !-week postinfusion samples and remained there for up to 1 month following therapy, with an average of 3.4 for three of the courses. The H/S ratios correlated weakly with the clinical status of the patients, in that the patients with lower H/S ratios showed longer time courses of improvement than did the patients whose H/S ratios returned to pretherapy levels.

The absolute numbers of circulating lymphocytes decreased during therapy for five of the seven therapy courses (patients 1, 2a, 2b, 4b, and 5: Table

Journal of Clinical Immunology, Vol. 8, No.l, 1988

EFFECTS OF IgG ON BLOOD CELLS IN MYASTHENIA GRAVIS 27

I ! l ~ -

6 o o o -

4 0 0 0 -

2 o o o -

3S.0 '

! ! / ' " x, ' / /

+

# # # # # o i ~ i ~ l J i . - - o + - - i i J t l ; - + - - - o + i ~ i t

1 2 ,3 .4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 0

( D A Y S )

Fig. 2. The changes in serum IgG levels in five patients during and following seven courses of infusion demonstrating a two- to four-fold increase. Filled symbols (circles and squares) represent the second course of IV IgG in each of two patients. Arrows as defined in the legend to Fig. 1.

I). The absolute numbers of T helper cells de- creased in all five cases and the absolute numbers of T suppressor cells decreased in three of the cases

(Table II). Since the NK cells which increased dramatically during the therapy would be expected to have the T suppressor cell surface marker (see

2 9 . 2

6.8

A

- J 23 .3 ..J UJ r,.)

LL. 0

1 7 . 5

l - - Z uJ O r r MJ 1 1 . 7 r , . . . . . . . . / " / T'x,~

- - ~ " " ~ . < . . < -< " " ~ ~ ~ ~ ~ ~ - ' : . l l t ' ~ . . . . . . . . . . \

t t t t t 1 2 3 4 ,5 6 1 2

( D A Y S )

Fig. 3. The changes in the percentage of mononuclear cells contained with antiim- munoglobulin in five patients during and following seven courses of infusion. Normal range, 6 to 13%. Arrows as defined in the legend to Fig. 1.

Journal of Clinical Immunology, Vol. 8, No.I, 1988

28 COOK, HOWARD, AND FOLDS

35 .0

29 .2

CO • -J 23.3 i I u,I (.~

fJ. O

17.6 i I

Z LU t,3 n,-

11.7 rl

6,0

/' Y.,

/ / i .....

//' • / ' ' 'm

i f ~'\~.i ?--- 5, \ , , . . . . . . . . . . . . . . . . . . , , \ i ! '"'-~..X . - . - . . . . . . . . . - - J J ~

~,lli \ ~ .... ." --.. ~ J ',:\ \ .." ~ " ' . . . .

1 6 1 1 1 6 2 1 2 6 3 1 ( D A Y S )

Fig. 4. The changes in the percentage of mononuclear cells stained with the Leu 11 (NK) monoclonal antibody in five patients during and following seven courses of infusion. Normal range, 4 to 9%. Arrows as defined in the legend to Fig. 1.

above), a profound T suppressor cell decrease may be masked by an increase in circulating NK cell numbers. Absolute numbers of lymphocytes re- turned to baseline levels within a week of following therapy. The three patients with long-term lowered

HIS ratios showed decreased absolute numbers of T helper cells as compared to the preinfusion sam- ples.

The single initial sample with a H/S ratio of 1.5 was drawn from a patient previously treated with

4 . O

8.1t ~ / ~ + /" / "/ / * / /"

I I . O ".. /

~ \ ~ L / / \, . ." L \ ~2-~.Y2~..r-__ "', /" - ~ , _ . . . . . . . .

\ ~ ' - ~ ' . - . z . . . . . . . rr a . o ~ ' - , , . , . ~ / ..........

~ ., .....; V '"... i ......................... "'"

1,0

.11-

0 ~ ~ l l : : : : : ; ~I 1 1 : : 1 : : 1 1 1 1 1 1 I I i i l t 1 I |

1 O 11 l e 2 1 2 0 3 1 ( D A Y S )

Fig. 5. The changes in the helper/suppressor ratio of five patients during and following seven courses of infusion. Normal range, 1.5 to 3.1. Arrows as defined in the legend to Fig. 1.

'"D

Journal of Clinical Immunology, Vol. 8, No.l, 1988

EFFECTS OF IgG ON BLOOD CELLS IN MYASTHENIA GRAVIS 29

Table II. Changes in Absolute Numbers of T Cell Subsets

Absolute count

Patient Day T helpers T suppressors H/S ratio a

1 1 0.91 0.39 2.3 5 O.49 021 2.3

18 0.68 0,33 2.1 2a 1 1.00 0.32 3.1

6 0.50 0.27 1.9 26 0.15 0.26 0.5

2b 1 0.91 0.60 1.5 5 0.56 0.37 1.5

12 0.76 0,40 1.9 3 1 1.27 0,43 2.9

6 1.52 0,53 2.8 12 1.78 0.50 3.6

4a 1 0,97 0.27 3.5 5 0,79 0.23 2.6

12 1.22 0.36 3.4 4b 1 1.40 0.43 2.9

6 0.36 0.23 1.6 19 1.00 0.32 3. I

5 1 0.61 0,21 2.8 5 0.33 0.14 2.2

12 0.52 0.24 2.1

°H/S ratio calculated by (% l~eu 3 cells)l(% Leu 2 cells),

~-globulin 84 days prior to the second course. The initial course of therapy had shown a decrease in the H/S ratio from 3.1 to 1.7 and the ratio remained below 2.0 for the follow-up samples. The H/S ratio did not significantly change during the second course of treatment (1.5-2.5), despite a marked worsening of the clinical status of the patient.

D I S C U S S I O N

Clinical improvement in the strength of myas- thenic patients has previously been reported follow- ing infusion of -c-globulin (18-21) and our data support these findings. The mechanism of action of the ~-globulin in this patient population is currently unknown. Our studies have shown that a transient decrease in PMNs and lymphocytes occurred dur- ing the week of therapy and that the WBC returned to preinfusion levels in the week following treat- ment. This transient decrease is similar in magni- tude to the decrease in PMNs seen uncommonly in patients with systemic lupus erythematosus treated with ~/-globulin (14, 28). A decrease in peripheral blood PMNs has not been reported in studies of other types of patients given intravenous ~/-globu- lin. The mechanism of decrease in the numbers of PMNs seen in our patients is unknown. It is possi- ble that the infused IV IgG was either passively absorbed to or specifically bound to the PMN cell

membranes and that this absorbed immunoglobulin led to the removal of the PMNs from the circula- tion.

The absolute numbers of lymphocytes decreased slightly during therapy. These data are consistent with the reports of decreased lymphocyte numbers in adult idiopathic thrombocytopenic purpura pa- tients given IV IgG therapy (27, 28). Two different kinds of changes were seen in the lymphocyte subsets of our patients. The first was an increase in cells positive for the Leu 11 (CD16) monoclonal antibody. The highest numbers of Leu I1 (CD16) cells were found when the highest levels of IgG were present in the serum. In a few patients, cells with low expression of the Leu 2 (CD8) antigen also increased at the time the Leu 11 (CD16) cells were high. Since NK cells express the Leu 11 (CD16) antigen and weakly express the Leu 2 (CDS) anti- gen, it is possible that the high-dose immunoglob- ulin stimulates either proliferation of or redistribu- tion of NK cells as do other immunologically re- lated substances such as -i-interferon and interlu- kin-2 (29, 30).

An increase in surface immunoglobulin-positive cells was also seen at the same time and with a similar magnitude (about 10%) as the increa,~e in NK cells. This increase in surface immunoglobulin was not due to an increase in circulating B cells, since the percentages of ceils positive with mono- clonal antibodies that stain normal B cells, Leu 12 (CD19), and HLA-Dr did not increase. Since stain- ing of the cells with antiimmunoglobulin class- specific antisera showed that about half of the surface immunoglobulin-positive cells were stained with anti-IgG, and IgG-positive B cells are normally in low numbers in human peripheral blood, it is probable that a subset of lymphocytes passively acquired IgG from the serum when the serum IgG was high. Injection of myeloma proteins into mice and rats leads to an increase in suppressor T cells with Fc receptors specific for the class of myeloma protein injected (31, 32). This effect has been re- ported to be dose related and seen only when significant elevations in the quantity of circulating myeloma protein were achieved. It is therefore possible that the numbers of cells with IgG-specific Fc receptors increased in the peripheral blood of the patients as the serum IgG levels increased. Whether these Fc receptor-positive cells are T cells or NK cells cannot be determined by the methods currently employed in this study. In summary, it is probable that approximately 10% of the lympho-

Journal of Clinical Immunology, VoL 8, No.l, 1988

30 COOK, HOWARD, AND FOLDS

cytes present in the 24-hr postinfusion samples were T cells of NK cells with IgG bound to their membrane via Fc receptors.

We observed long-term changes in helper/sup- pressor cell ratios with three of our patients, while the ratios returned to pretherapy levels in the re- maining patients. This long-term change appeared to be due to decreases in the absolute numbers of T helper cells. Because of low sample numbers, this observation must be confirmed by additional stud- ies. Studies should focus on long-term changes seen in some individuals and the determination of abso- lute numbers of T helper cells in the peripheral blood and other lymphoid tissues.

The clinical improvement in patients given IV IgG has been ascribed to a wide variety of effects on the immune system: activation of suppressor T cells which shut down autoantibody production (28, 33, 34), activation or inhibition of monocytes (34, 35), direct inhibition of B cells (34), alteration in phago- cyte function (36), stimulation or suppression of cells bearing Fc-¢ receptors by anti-Fc~ R antibod- ies present in IV IgG (7, 37), stimulation of suppres- sor T cells by immune complexes (38), and antiidi- otype antibodies complexing with the circulating autoantibody or antiidiotype effects on B and T cells (10).

In our studies, clinical improvement was seen early (3-12 days) in most of the patients and a continued long-term improvement (2-3 months) was seen in three patients. Since the immediate improvement takes place before circulating levels of anti-AChR change, but has a time course similar to the response of myasthenic patients to plasma exchange, any proposed mechanism must account for rapid improvement in the presence of anti- AChR. Further study is necessary to determine if any of the current hypothesis can account for the rapid improvement or if additional mechanisms may explain the improvement.

The long-term improvement seen in some of the myasthenic patients may be due to stimulation of T suppressor cells; this hypothesis is supported by the changes we observed in the H/S ratios of some of our patients. Further studies are necessary to de- termined whether this stimulation is due to immune complexes, antiidiotype antibodies, anti-Fc~/recep- tor antibodies, or perhaps suppressive effects of NK cells. Since the suppressive effects are not antigen specific (28) and myasthenic patients are deficient in AChR-specific suppressor cells (39), the clinical improvement seen in myasthenic patients

may be temporary. Additional studies are necessary to determine if multicourse therapy can improve the clinical response to IV IgG by myasthenic patients.

ACKNOWLEDGMENTS

The authors express their thanks to Professor Dana Quade for his assistance in performing the statistical analyses.

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Journal o f Clinical Immunology, Vol. 8, No.l , 1988