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Prithvi M.Sc. Bioinformatics - IICell Mediated & Humoral Immunity

Cell Mediated ImmunityUnlike humoral immunity, which is designed to react against extracellular antigens, cell-mediated immunity is much better at recognizing and eliminating microbes that are within cells.

Major key players :

MHC I & MHC II CD4 & CD8 proteinsHelper & Cytotoxic T cellsAntigen Presenting Cells ( APC )T Cell Receptors ( TCR )

Type of T cell activatedMHC class I activates CD8 +T cytotoxic cells

Present endogenous (eg viral) antigens

Target cell is killed by CD8 cell

Any cell can become virally infected

Therefore: MHC class I is on all nucleated cells

Type of T cell activatedMHC class II activates CD4 +T helper cells

Present exogenous (eg bacterial) antigens

CD4 T cells upregulate all immune functions

MHC class II found only on cells that sample the extracellular environment

Humoral ImmunityThe humoral immune response begins with the recognition of antigens by nave B cells.

These cells then undergo a process of clonal expansion and differentiation. Through this process, the B cell matures into antibody secreting plasma cells, which secrete antibodies.

Finally, as this response declines, a pool of memory cells remains behind. If the body is re-exposed to the antigen, these memory cells will recognize the antigen and respond much more quickly and effectively.