immune response to microbes

• pregnancy

  immune suppression, hormonal regulation, immune privilege
• extracellular bacteria (T cells)

  DC take up bacteria, exogenous antigen processing and presentation to CD4T cells, TH subsets are differentiated, cytokines trigger inflammation, activate macrophages, and help B cells produce antibodies
• extracellular bacteria (B cells and complement)

  antibodies neutralise bacteria and fungi, antibodies bound to antigens augment phagocytosis, complement coated bacteria augments phagocytosis, complement triggers inflammation, and bacteria is directly lysed by the MAC
• helminths

  too large to be ingested, Th2 and Tfh stimulate B cells to produce antibodies, antibodies (IgE) coat the parasite and stimulate mast cells (exocytose granules), eosinophils bind to helminths and release toxic granule contents, intestinal mucous secretion and peristalsis expell the worms. IL-4 and IL-13 contribute to tissue repair
• immunity to viruses

  IFN-1 induces an antiviral state, NK cells lyse virus infected cells, antibody can eliminate (neutralisation, opsonisation, complement activation, and ADCC) and CD8 CTL can kill infected cell. if mature virus particles are released, an antibody is required
• cytolysis induces apoptosis of infected cells
• co-stimulatory molecules

  CD28, 80, and 86
• immune checkpoint molecules

  PD1, PDL1, PDL2, CTLA-4