Immunity

Learning objectives

Describe how neutrophils and macrophages engulf and digest pathogens by phagocytosis, and distinguish self antigens from non-self antigens.

Describe the primary immune response, including antigen presentation by macrophages, clonal selection and expansion of B-lymphocytes into antibody-secreting plasma cells, and the roles of T-helper and T-killer cells.

Compare primary and secondary immune responses and explain how long-lived memory B and T cells make the second response faster and larger, giving lasting immunity.

Relate the structure of an antibody — two heavy and two light polypeptide chains joined by disulfide bonds, variable antigen-binding sites, a hinge region and a constant region — to its functions.

Outline how monoclonal antibodies are made by fusing plasma cells with myeloma cells to form hybridomas, and how their specificity is used to diagnose disease (for example pregnancy tests, locating tumours) and to treat it.

Distinguish active from passive and natural from artificial immunity, and explain how vaccines stimulate long-term immunity and how vaccination programmes control the spread of infectious diseases.