The cardinal features of inflammation are:.

Antigens (immunogens) are substances, usually proteins, that can be recognized by the body as foreign and can elicit an antibody response. Antigens are usually exogenous but may be endogenous...

Antibodies are produced by activated B-lymphocytes (plasma cells) and react specifically with the antigen that stimulated their production; they make up approximately 20% of the plasma proteins....

Cytokines are produced by many cell populations, but the predominant producers are helper T-cells (Th) and macrophages. Some cytokines (eg type 1 interferons [IFN] and tumour necrosis factor [TNF])...

Numbering of each component of the classical pathway of complement is from C1–C9. The sequence in which complement components are activated is C1, C4, C2, C3 and C5–C9 (since C4 was identified before,...

Antigen presenting cells are a heterogeneous group of immune cells that mediate the cellular immune response by processing and presenting antigens for recognition by T-cells. APCs are either:.

The main cells that mediate adaptive immunity are white blood cells (leukocytes) termed immunocytes – mainly lymphocytes:.

Innate defences include basic mechanisms resisting infections; predominantly including:.

The main primary organs of the immune system are lymphoid – the thymus and bone marrow (Figure 2) and secondary tissues such as spleen, tonsils, lymph vessels, lymph nodes, adenoids, skin and liver...