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Abstract
The thymus (central lymphoid organ) plays a crucial role in the development of the T cells in birds and mammals. Thymus provides an inductive microenvironment to the precursors of T lymphocytes, which are generated in the bone marrow except during the early fetal stage where they are generated in liver and spleen. T cells derived from bone marrow stem cells migrate at a very early stage to the thymus where functional and phenotypic maturation occur.
Cyclosporine- A (CsA) is a lipophilic cyclic undecapeptide isolated from the fungi Tolypocladium inflatum and Cylindrocarpon lucidium CsA has a powerful immunosuppressive effect, so it is used in transplantation medicine and to treat autoimmune diseases. Cyclosporine-A affects blunts T-cell responses by inhibiting nuclear factor of activated T cells-1 (NFAT-1) leading to reversible inhibition of transcription of interleukin-2 and several other cytokines, most notably in T helper lymphocytes. This reduces the production of a range of cytokines, inhibiting the activation and/or maturation of various cell types, including those involved in cell-mediated immunity.
This study was planned as an attempt to throw spot lights upon the effect of thymectomy and cyclosporine-A treatment on the nonspecific (monocytes function) and specific cell-mediated immune responses (resistance to experimental infection) in two months old-chickens.