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Leucocyte

T cells

Cytotoxic T cells recognize infected cell (by recognizing some antigen) and spur cell death.

Memory T cells

Reignite during secondary exposure.

B cells

When activated: Secrete antibodies.

Neutralizing antibodies bind to a virus and ensure that they can’t bind to cell receptors.
Non-neutralizing antibodies bind to antigens on surface of infected cells - detected by natural killer cells.

Plasma cells

Some B cells become plasma cells, which secrete antibodies for years.

Memory B cells

Can reignite antibodies during second exposure.

Natural killer (NK) cells

Goes where non-neutralizing antibodies from B cells have bound to antigens on surface of infected cells. Trigger apoptosis (cell death).