Avian cellular immune effector mechanisms ‐ A review

Abstract

Considerable new knowledge has accumulated within the last few years on the immune functions of birds, and data show that the avian cellular immune effector mechanisms are quite similar to those of mammals. Cellular immunity in the chicken, the most widely studied avian species, is primarily mediated by T cells, macrophages and NK cells. The avian T lymphocytes express unique surface antigens that distinguish these cells from other cells. The T cells respond vigorously in vitro to T cell-specific mitogens and can perform cytotoxic and mixed lymphocyte reactions against allogeneic or tumour cell targets. The in vivo responses mediated by T cells include allograft and tumour cell rejection, graft-versus-host reaction and delayed type hypersensitivity reactions. T cells also serve as helper cells in enabling B Cells to produce antibody against thymus-dependent antigens. Avian T cells also perform immune regulatory functions and sub-populations of T suppressor cells can cause profound blockage of antibody production by B cells. Certain T cell functions require cooperation from other immune cells, particularly major histo-compatibility complex-compatible macrophages. Avian macrophages resemble their mammalian counterparts in being adherent and phagocytic, and they serve as accessory cells in a multitude of immune reactions as well as effector cells in their own right. Macrophages when co-cultivated in vitro with tumour target cells may non-specifically arrest proliferation of tumour cells or lyse tumour cells. They may also engage in specific anti-alloantigen cytotoxicity following hyperimmunisation. Under certain circumstances, macrophages can also be potent suppressors of immune reactivity. Birds appear to have a well developed NK cell system. NK cells of chickens share general characteristics with mammalian NK cells and lack the surface markers of T cells, B cells, or macrophages. Recent evidence indicates that the NK cell system plays a role in defence against Marek's disease. NK-like cells have also been shown to mediate ADCC in chickens and ducks. The immunoregulatory factors that may mediate avian immune effector cell functions are currently being actively studied.

Cultivation and characterisation of avian lymphocytes with natural killer cell activity

“…In contrast to the mammalian NK cells, their avian counterparts have been poorly characterised (reviewed by Sharma and Tizard, 1984) and to our knowledge the cultivation of NK cells has not yet been reported. The limited amount of information available has been obtained with spleen cell populations.…”

Epidermal Tissue‐Derived T‐cell Growth Factor, Colony Stimulating Factor and Nerve Growth Factor in Chickens

“…It is thin in areas not covered with feathers and the epidermis is especially thin. It has been confirmed that delayed type hypersensitivity is induced in chickens (SHARMA and TIZARD, 1984). It is thus presumed that the KC produce cytokines in the skin of chickens, suggesting the existence of the same local immune system as in mammals.…”

Expressão espaço-temporal do sistema VEGF e do EG-VEGF no timo de cães

“…hipersensibilidade retardada e reações de hospedeiro versus enxerto, tal como comprovariam experiências à base de timectomia (FIRTH, 1977;GLICK, 1977;TIWARI;GOEL, 1985;SHARMA;TIZARD, 2000).…”

“…Porém, a timectomia origina uma ligeira redução na produção de anticorpos, podendo também não exercer sobre ela qualquer influencia (COOPER et al, 1965;DROEGE, 1971;FIRTH, 1977;SHARMA;TIZARD, 2000).…”