Reticular fibers

Fig. 14.1

Activate

Helper

T cells

B CellsCytotoxic

T cells

Help Activate

Help Activate

Cell mediatete

d immunity

antibody mediatete

d immunity

Figure 2. Activation of naive T-cells requires two independent signals. The binding of the peptide:MHC complex by the T-cell receptor and, in this example, the CD4 co-receptor transmits a signal (signal 1 indicated by arrow 1) to the T-cell that antigen has been recognized. Activation of naive T-cells requires a second signal (signal 2 indicated by arrow), the co-stimulatory signal, which is delivered by the same antigen-presenting cell (APC). From Janeway CA, Jr., and Travers P. Immunobiology. 2nd edition, 1996, pp. 7:8, with permission from the publisher, Current Biology, Ltd, London.

Cellular interactions involved in induction of immune responses. Activation and proliferation of TH cells. (a) is required for generation of humoral response (b) and cell-mediated response to altered self-cells (c). APC = antigen-presenting cell; Ag =

antigen.

                                                                                                                                                                                  

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Helpful animations

Helper T cells 1 & Helper T cells 2

T independent imm unity T dependent imm unit yH elper T cells no t invo lved

A ntigens are usually lip ids o r carbohydrates

No m em ory cells m ade

D evelops after age 2

H elper T cells invo lved

A ntigens are usually pro teins

Mem ory cells m ade

C an occur at b irth