Immune response only means, the response of our immune system to some foreign body entering the Human body. The procedures concerned with the immune response are: Cell mediated immunity, humoral immunity, antibody dependent cell-mediated immunity, NK cells- Natural Killer cells mediated immunity, and Macrophages-mediated immunity.
Cell mediated Immunity
This is mediated by the T cells. A. Immunity against infections: Effective immunity against bacteria such as mycobacteria and listeria, certain viruses and just about all parasites is mediated by T cells. T cells from sensitized individuals lyze the target cells bearing the viruses.
- Helper function: Helper cells (TH) are a subgroup of cells with receptors for the Fc part of IgM (Tu). They form about 50% of the T cells of peripheral blood. They are necessary for optimum antibody generation by plasma cells and for generation of cytotoxic T cells.
- The rejection of allograft and destruction of tumor cells: These can also be mediated mainly by T cells, although other mechanisms are also included.
- Suppressor function: The suppressor cell (TS) subgroup which comprises 10 percent of this total can be separated by the presence of surface receptors for Fc part of IgG (Tr). They regulate the actions of both B and T cells. The TS activity is depressed in several autoimmune diseases and in some of the human malignancies.
- Production of soluble mediators: T cells, stimulated by antigens, liberate certain soluble substances called lymphokines. Lymphokines include macrophage migration inhibition factor (MIF), macrophage activation factor (MAF), leucocyte migration inhibition factor (LMIF), leucocyte adherence inhibition factor (LAIF), chemotactic factor, transfer factor and interferon. The MIF and MAF assist in the accumulation of macrophages at the site of reaction. The subsequent erythema and induration form the basis of skin tests. Administration of transfer factor to non-sensitized people contributes to specific sensitization. Interferon interferes with virus multiplication in host cells.
- Delayed hypersensitivity: When tuberculin (or a similar antigen) is injected intradermally in sensitized person, an erythematous indurate lesion develops gradually, reaching its maximum within 48-72 hours. This is called delated sort of hypersensitivity. Hypersensitivity is the abnormal over-reaction of the immune system and it usually leads to un-wanted tissue destruction. This accounts for caseation in the case of tuberculosis, granulomatous skin lesions in tuberculoid leprosy, rashes in smallpox and measles, skin lesions in herpes simplex, and contact hyper-sensitivity to plants and compounds. Hypersensitivity reaction mediated by T cells is known as type IV reaction.