Types of Immunity

Phagocyte recognises a foreign antigen on a pathogen

Phagocyte binds to and engulfs the pathogen and keeps it in a vesicle called a phagosome

Lysosomes bind to the phagosome and release digestive enzymes which hydrolyse the pathogen

The phagocyte releases the cell debris and presents the foreign antigen on its surface

Phagocytosis

Cell Mediated Immunity

T helper cells have receptors on their surface and respond to the invasion of own cells invaded by non-self material

They bind to an antigen presenting cell

They release chemicals called cytokines

Cytokines activate cytotoxic T-cells and B-cells

Cytotoxic T-cells kill infected cells by using perforins to make holes in the cell, causing it to burst

Some T-cells may clone into memory cells, so their receptors are complementary to this antigen if it infects again

Humoral Immunity

Antigens on the surface of the pathogen are taken up by B cells

B-Cells present the antigen on their surface

A T-cell with a receptor complementary to the antigen binds to it

This activates the B-cell, causing it to replicate by mitosis and produce plasma cells

These plasma cells produce antibodies complementary and specific to the antigen

The antibodies have a specific variable region which binds to antigens, grouping the pathogens together so they can be destroyed