Immunohistochemical study of the local inflammatory infiltrate in spontaneous canine transmissible venereal tumour at different stages of growth

Immunohistochemical expression of B and T-lymphocytes and TGF-β in experimentally transplanted canine venereal tumor

“…The findings from the present study and those of PÉREZ et al (1998) are different from those reported by CHANDLER & YANG (1981). These authors characterized the lymphocytic infiltrate of TVT during the regression phase and observed that, during this phase, 60% was T-lymphocytes, 26% Blymphocytes and 14% null cells.…”

“…This result was similar to what was presented by PÉREZ et al (1998), who demonstrated significantly increased numbers of B cells in tumors during the regression phase, in comparison with the progression phase. The high number of B cells found in the infiltrate of transplanted tumors in the regression phase and the low number of these cells in the progression phase of TVT suggested that the local tumor immune response may have an important role in the spontaneous regression of this neoplasia (PÉREZ et al, 1998).…”

“…This led them to suggest that factors present in the serum of dogs with TVT might inhibit the proliferation of lymphocytes and consequently facilitate tumor growth during the progression phase. PÉREZ et al (1998) also found that CD3 + T-lymphocytes were expressed in large quantities during the regression phase, thus coinciding with the report by MIZUNO et al (1989), which led them to suggest that these cells might participate in tumor regression. This could not be confirmed from the present study, considering that CD3 + T-lymphocytes were found at similar concentrations in the progression and regression phases of the transplanted TVT.…”

“…It can also be transmitted experimentally (YANG & JONES, 1973;YANG et al, 1991;TINUCCI-COSTA, 1999). Studies have demonstrated that greater expression of CD3 Tlymphocytes (MIZUNO et al, 1989;PÉREZ et al, 1998), CD4 andCD8 T-lymphocytes (GONZALEZ et al, 2000), B-lymphocytes, macrophages and the major histocompatibility complex (YANG et al, 1987;PÉREZ et al, 1998) are associated with the regression phase of TVT.…”

Reversible epigenetic down-regulation of MHC molecules by devil facial tumour disease illustrates immune escape by a contagious cancer

“…After transmission of CTVT, tumors appear within 2 mo and cells undergo an initial growth stage where the tumor cells lack expression of class I and class II molecules, and lymphocytes fail to infiltrate the tumor (6,15). This period of tumor growth does not continue indefinitely, and after 3 to 9 mo, tumor growth either stabilizes or begins to regress, which is associated with a significant increase in MHC class I and class II expression on the surface of the CTVT cells and infiltration of lymphocytes into the tumor mass (6,15). Outside the laboratory setting, CTVT tumors often enter a stationary phase in which the tumor neither grows nor regresses (5).…”