Cells under attack release histamine --> attracts macrophagesMacrophage engulfs pathogen into a phagocytic vacuole by phagocytosisMacrophage carries out antigen presentation of pathogenic antigen from cell surface membrane of pathogenT cell with complementary receptor detects pathogenic antigen by clonal selectionThis T cell stimulates the production of further T cells (clonal expansion)1) T killer cells: inject hydrogen peroxide into pathogenic cell2) T memory cells: remain in blood & provide immunological memory3) T helper cellsT helper cells release cytokines --> activate specific B cells to produce 2 types of B cell by clonal expansion:1) B memory cells: provide immunological memory2) Plasma cells: produce complementary antibodies to pathogenic antigen