Lymphocyte-mediated type hypersensitivity

Large numbers of activated macrophages surround the solid caseous (cheese-like) TB foci (the necrotic area) as a part of cell-mediated immunity. Delayed-type hypersensitivity also develops through activation and multiplication of T lymphocytes. Macrophages form granulomas to contain the organisms. 

Cell-mediated immunity Cytotoxic T lymphocyte killing delayed type hypersensitivity response mouse ear swelling test (MEST Gad et al., 1986) guinea pig maximization test (Magnusson and Kligman, 1969). 

Anti-lymphocyte globulin (ALG) has been prepared as an highly purified solution of y-globulins with antilymphocyte activity by immunizing horses with human lymphocytes. It activates complement-mediated destruction of lymphocytes and thus decreases cellular immunity with only a limited effect on humoral immunity. Anti-lymphocyte globulin suppresses delayed type hypersensitivity reactions. It is used for the prevention and treatment of rejection episodes of transplanted organs. It also has some indication for the management of idiopathic aplastic anemia. Adverse effects include pain at the site of injection, erythema, serum sickness and rarely anaphylactic shock and thrombocytopenia. 

In experimental mouse studies, TCDD exposure results in thymic atrophy and alterations in an array of adaptive immune responses including delayed-type hypersensitivity (DTH), cytotoxic T lymphocyte (CTL) activity, and T-cell-dependent antibody responses. In contrast, TCDD enhances neutrophil recruitment to the site of antigen challenge. Because both cell-mediated and humoral immunity are suppressed by TCDD and related HAHs, it is not surprising that administration of these compounds to mice results in increased susceptibility to challenge with viral, bacterial, or parasitic diseases, as well as syngeneic tumors. 

At the same time that CMl occurs, delayed-type hypersensitivity (DTH) also develops through the activation and multiplication of T-lymphocytes. DTH refers to the cytotoxic immune process that kills nonactivated immature macrophages that are permitting intracellular bacillary replication. These immature macrophages are killed when the T-lymphocytes initiate Fas-mediated apoptosis (programmed cell death). The bacilli released from the immature macrophages then are killed by the activated macrophages. ... 

In order to fully understand the complex biochemical mechanisms by which the thymus and its hormones control the expression of immunity, it is first necessary to review briefly the organization of the thymus-dependent (T cell) immune system (Fig. I). The predominant cells of the peripheral lymphoid tissue (i.e., spleen, lymph nodes) includes both B and T lymphocytes. In the presence of foreign antigens, B lymphocytes differentiate into plasma cells, which in turn synthesize antibody thus, B cells make up the humoral arm of the immune system. In contrast, T lymphocytes are responsible for mediating all the classical cellular immune responses such as delayed type hypersensitivity skin responses, organ transplant rejections, and sensitized antitumor immunity as well as immunity toward various viral, fungal, and protozoal pathogens (Reinherz and Schlossman, 1980). 

Various investigators (Halpern et al. 1967 Federlin et al. 1969 Federlin 1971 Feinglos and Jegasothy 1969 Faulk et al. 1975 MacCuish et al. 1975 Diem and Teuscher 1979 Diem et al. 1982) have shown that insulin of porcine or bovine origin can induce lymphocyte transformation in lymphocytes from diabetic patients with both immediate- or delayed-type hypersensitivity to commercial insulin. Such cell-mediated reactions to insulin in vitro have also been reported in untreated diabetics they are rather common in insulin-treated diabetics even without any evidence of allergy in vivo (MacCuish et al. 1975). 

---