T cells and C cells binding

T cells first step:

dendritic cell engulfs a bacterium

T cells second step:

large molecules of engulfed bacterium are broken down by lysosomes to produce antigenic peptides

T cells third step:

New MHC molecule has been synthesized by endoplasmic reticulum-golgi complex

T cells fourth cell:

antigenic peptides bind to newly formed MHC molecules

T cell fifth step:

antigen is displayed on cell surface bound to MHC moecule-cell is now an antigen-presenting cell(APC)

Cytotoxic T cells first step:

class I MHC molecules are found on surface of all cells

Cytotoxic T cells second step:

they are recognized only by cytotoxic(CD8+) T cells

Cytotoxic T cells third step:

CD8 coreceptor links the two cells together

Cytotoxic T cells fourth step:

Linked in way, cytotoxic T cells can destroy body cells if invaded by foreign(viral) antigen

Helper T cell first step:

Class II MHC molecules are found on surface of immune cells with which helper T cells interact: denticity cells, macrophages, and B cells

Helper T cell second step:

They are recognized only by helper(CD4+) T cell

Helper T cell third step:

CD4 coreceptor links the 2 cells together

Helper T cell fourth step:

To be activated, helper T cells must bind with a class II MHC-bearing APC(dendritic cell or macrophage) To activate B cells, helper T cell must bind with class II MHC- bearing B cell with displayed foreign antigen