Page "Macrophage" Paragraph 11

The antigen presentation on the surface of infected macrophages ( in the context of MHC class II ) in a lymph node stimulates TH1 ( type 1 helper T cells ) to proliferate ( mainly due to IL-12 secretion from the macrophage ).

When a B-cell in the lymph node recognizes the same unprocessed surface antigen on the bacterium with its surface bound antibody, the antigen is endocytosed and processed.

The processed antigen is then presented in MHCII on the surface of the B-cell.

T cells that express the T cell receptor which recognizes the antigen-MHCII complex ( with co-stimulatory factors-CD40 and CD40L ) cause the B-cell to produce antibodies that help opsonisation of the antigen so that the bacteria can be better cleared by phagocytes.