Cellular immunity To Viral Infection

·         This arm of acquired immunity serves to get rid of the antigen which present intracellularly.

·         The only way to do that is to kill the cell harboring the antigen. (virus infected cells- tumor cells and transplanted cells).

·         Main cell carry this function is T cytotoxic cell.

·         Tc cell require the signals of T helper cells including: IL2-IFN Ɣ -

T-cytotoxic cells- 1

·         Arises from stem cells in bone marrow and migrate to thymus to maturate.

·         Maturation involves rearrangment genes encoding TCR, so any T cell produce only one kind of TCR that matches only one or few antigens.

·         Once maturate, T cells migrate to blood stream and lymphatic system.

·         Tc cells carry a protein on their surface known as CD8 which help recognition of MHC class I.

·         If they bind with antigen presented by MHC I of infected or altered self cells, and if T helper cells send the proper signals mainly: IL2-IFN Ɣ

·         Tc cells become activated and divide

·         Some progeny become effecter cells, live shortly and produce large quantities of chemicals break open infected cells and kill it through:

·         Binding T_C cells to the target cell and release perforin into its membrane Ganzym enzyme

·         In the presence of Ca²⁺, perforin causes cell lysis by creating transmembrane pores

·         then Ganzym enter the pores hydrolyses the nucleic acid of infected cell

T-cytotoxic cells- 2

·         Other progeny become long-lived memory cells and stay in the body for years with the potential to become activated with subsequent exposure to antigen.