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Before an invading microbe can be eliminated form the body by the immune system these steps must take place: 1 .A macro'phage is activated to phagocytize the offending particle and present antigen to T and B lymphocytes. 2. Activated T -cells synthesize and secrete . cytokine. 3. B- cells are activated bya T -cell cytokine and antigen from a pathogen. . 4. Activated B-cells may become either a plasma cell or a B-memory cell. 5. Plasma cells synthesize and secrete immunoglobin. 6. Immunologic memory is established when specific B-memory cells and T- cells form a specific clone dedicated to protecting the body against a specific antigen. 7. Acquired immunity is very effective but takes days or weeks to establish. The presence of a specific immunity clone reduces the time from pathogenic challenge to protection .
The structure of the receptor for T cells. Fig. 15.6 Proposed structure of the T cell receptor for antigen.
The Class I and II MHC for humans are surface receptors consisting of glycoproteins. Fig. 15.2 The human major histocompatibility complex.
Characteristics of the different subsets of T cells. Table 15.3 Characteristic of subsets of T cells.
The stages of B-cell activation and antibody synthesis. Run Animation: Antibody diversity Fig. 15.10 Events in B-cell activation and antibody synthesis.
An example of helper and cytotoxic T cell activation and differentiation. Fig. 15.16 Overall scheme of T-cell activation and differentiation into different types of T cells.
An example of a cytotoxic T cell destroying a cancer cell. Fig. 15.17 A cytotoxic T cell has mounted a successful attack on a tumor cell.
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