Abstract
The mammary tumor study in female dogs is revealed as an excellent model for the investigation of breast tumors in humans. Malignant tumors reflect antigens that stimulate and serve as targets for tumor immunity. The innate immune system includes neutrophils, macrophages, dendritic cells and NK cells. The NK cells activity against tumor cells is correlated with reduced or no expression of MHC class I, inducing cytolysis of target cells. The acquired immune system develops participation through adaptive immunity, composed of B and T lymphocytes and co-participation of cell of innate immunity. Lymphocytes T CD4 secrete cytokines capable of activating other immune cells such as CD8 cytotoxic T cells that destroy cells infected by intracellular microorganisms. The proliferation and differentiation of T cells require signals provided by molecules of the APCs (antigen-presenting cells), called co-stimulators, B7-1 (CD80) and B7-2 (CD86), which can link to CD28, express on T helper cells, promoting T cells activation and making them to proliferate and produce cytokine, or may link to CD152, also expressed in the helper T cell, inhibiting their activation. Another form of negative regulation of the immune system are the Tregs, that inhibit activation of T cells (CD4 and CD8) and antigen-presenting cells (APCs), representing approximately 5% of CD4 T lymphocytes from peripheral blood, characterized by the expression constituent molecules FOXP3, GITR, CTLA-4 and high levels of CD25. This study aims to evaluate the expression using immunohistochemistry, lymphocyte infiltration (CD4, CD8, CD4+CD25+, CD28, CD80, CD86, CD152 and NK) in canine mammary carcinosarcoma in order to detect the efficacy of stimulation and immune system defense in this tipe of neoplasia, that represent the majority of malignant mammary tumors diagnosed in female dogs. (AU)