AimsAims

State the normal functions of the State the normal functions of the immune system.immune system.

State the primary and secondary State the primary and secondary lymphoid tissues and their functions.lymphoid tissues and their functions.

Readings: Abbas & Lichtman, Readings: Abbas & Lichtman, Chapter 1Chapter 1

ImmunityImmunity

From the Latin From the Latin immunisimmunis meaning meaning exemptexempt

Immunity refers to all the Immunity refers to all the mechanisms used by the body as mechanisms used by the body as protection against foreign protection against foreign environmental agentsenvironmental agents

Normal Functions of the Immune Normal Functions of the Immune SystemSystem

Protect from infectious disease or re-Protect from infectious disease or re-infectioninfection• Prevent entry/access of microorganismsPrevent entry/access of microorganisms• Prevent or inhibit growth of microorganisms Prevent or inhibit growth of microorganisms

(Fe(Fe++++))• Neutralize toxins Neutralize toxins • Kill or destroy infectious agentsKill or destroy infectious agents• Sequesters (‘walls-off’) infectious agentsSequesters (‘walls-off’) infectious agents

Removes effected cells and cellular debrisRemoves effected cells and cellular debris Surveillance for neoplastic cellsSurveillance for neoplastic cells

Normal Functions of Immune Normal Functions of Immune SystemSystem

TheThe physiologic functionphysiologic function of the immune of the immune system is tosystem is to prevent infections and prevent infections and eradicate established infectionseradicate established infections..

AIDS has demonstrated how important the AIDS has demonstrated how important the immune system really is.immune system really is.

Abbas & Lichtman’s Basic Immunology 1-1

Normal Functions of Immune Normal Functions of Immune SystemSystem

Vaccinations are effective because they stimulate an Vaccinations are effective because they stimulate an immune response to microbes and prime the immune immune response to microbes and prime the immune system for a potential infection by that microbe.system for a potential infection by that microbe.

Vaccines have eradicated certain infectious diseases.Vaccines have eradicated certain infectious diseases.

Abbas & Lichtman’s Basic Immunology 1-2

VaccinesVaccines

• Are vaccines safe? - the pertussis Are vaccines safe? - the pertussis paradigmparadigm 2 children die in Japan soon after 2 children die in Japan soon after

receiving the whole cell pertussis vaccine receiving the whole cell pertussis vaccine in 1974. That year there were no deaths in 1974. That year there were no deaths related to pertussis.related to pertussis.

1974 - 1979 there was a >1300% increase 1974 - 1979 there was a >1300% increase in pertussis cases. In 1979, 41 children in pertussis cases. In 1979, 41 children died of pertussis in Japan.died of pertussis in Japan.

An acellular pertussis vaccine now exists An acellular pertussis vaccine now exists which has eliminated the alleged offending which has eliminated the alleged offending antigen.antigen.

VaccinesVaccines• Are vaccines safe? - the MMR vaccineAre vaccines safe? - the MMR vaccine

Finnish study from 1982 - 1996.Finnish study from 1982 - 1996. 1.8 million individuals vaccinated 1.8 million individuals vaccinated

with 3 million vaccine doses.with 3 million vaccine doses. 173 potentially serious reactions, 173 potentially serious reactions,

with 1 death.with 1 death. 77 neurologic77 neurologic 73 allergic73 allergic 22 miscellaneous22 miscellaneous 3.2 serious events per 100,000 vaccines 3.2 serious events per 100,000 vaccines administered.administered.

VaccinesVaccines

Why vaccinate?Why vaccinate?

Normal Functions of the Immune Normal Functions of the Immune SystemSystem

The majority of microorganisms that are The majority of microorganisms that are encountered are destroyed quickly by the encountered are destroyed quickly by the innateinnate (non-specific) immune system (non-specific) immune system these do not induce an these do not induce an adaptiveadaptive

(specific) immune response(specific) immune response

Immune specificity – cells that are capable Immune specificity – cells that are capable of attacking influenza virus are not of attacking influenza virus are not necessarily adept at killing streptococcal necessarily adept at killing streptococcal bacteriabacteria

Abnormal Functions of the Abnormal Functions of the Immune SystemImmune System

AutoimmunityAutoimmunity – immune reaction to – immune reaction to selfself

Immune pathologyImmune pathology – often a – often a consequence of the immune consequence of the immune responseresponse Collateral damage pathology Collateral damage pathology HypersensitivitiesHypersensitivities Immune deficienciesImmune deficiencies

Cells and Tissues of the Immune Cells and Tissues of the Immune SystemSystem

The major players are the The major players are the leukocytesleukocytes (WBCs)(WBCs)

Primary lymphoid tissues give rise to Primary lymphoid tissues give rise to leukocytesleukocytes

1.1. Bone marrowBone marrow major site of leukocyte, erythrocyte (red major site of leukocyte, erythrocyte (red

blood cell) and platelet developmentblood cell) and platelet development all bone marrow-derived cells arise from a all bone marrow-derived cells arise from a

pluripotent stem cellpluripotent stem cell2.2. ThymusThymus

encapsulated organ lying anterior to the encapsulated organ lying anterior to the heart within the rib cageheart within the rib cage

site of further maturation by a select group of site of further maturation by a select group of bone marrow cells – T-lymphocytesbone marrow cells – T-lymphocytes

Cells of the Immune SystemCells of the Immune System

Abbas & Lichtman’s Basic Immunology 1-11

Maturation of LymphocytesMaturation of Lymphocytes

Lymphocytes develop from precursors in the Lymphocytes develop from precursors in the generative (1generative (1) lymphoid organs.) lymphoid organs. Bone marrow for B lymphocytesBone marrow for B lymphocytes Thymus for T lymphocytesThymus for T lymphocytes

Abbas & Lichtman’s Basic Immunology 1-12

Stem Cell

Bone Marrow

Thymus

Blood

Blood,Lymph

Lymph nodes

Spleen

Mucosal andCutaneousLymph tissue

Maturation of LymphocytesMaturation of Lymphocytes

Mature lymphocytes enter the peripheral Mature lymphocytes enter the peripheral lymphoid organslymphoid organs (lymph(lymph nodes, spleen, & nodes, spleen, & other lymphoid tissues) where theyother lymphoid tissues) where they respond to foreign antigens and respond to foreign antigens and recirculate into the blood and lymphrecirculate into the blood and lymph..

These locations are the 2These locations are the 2 lymphoid tissues lymphoid tissues Here, lymphocytes can interact with other Here, lymphocytes can interact with other

leukocytes and undergo differentiationleukocytes and undergo differentiation

Maturation of LymphocytesMaturation of Lymphocytes

Abbas & Lichtman’s Basic Immunology 1-12

Stem Cell

Bone Marrow

Thymus

Blood

Blood,Lymph

Lymph nodes

Spleen

Mucosal andCutaneousLymph tissue

Secondary (2Secondary (2oo) Lymphoid ) Lymphoid TissuesTissues

Lymph nodesLymph nodes SpleenSpleen Mucosa-associated lymphoid tissue Mucosa-associated lymphoid tissue

(MALT)(MALT) Pharyngeal tonsilsPharyngeal tonsils Peyer’s patchesPeyer’s patches lunglung lamina propria of GI tractlamina propria of GI tract

Roitt’s Immunology 7-2