MHCII Expression on Peripheral Blood Monocytes in Canine Lymphoma: An Impact of Glucocorticoids

SIMPLE SUMMARY: Loss or decreased expression of human leukocyte antigen—D-related (HLA-DR) on the surface of monocytes is related to the dysfunction of the immune system and was reported in human neoplasia, including lymphoma. Canine lymphoma is frequently presented as a valuable comparative model for studies on human non-Hodgkin’s lymphoma. However, there are no studies on the expression of analogue proteins—MHCII antigens—on monocytes in canine lymphoma. In this study, we have evaluated the changes in the expression of MHCII on monocytes in the blood of dogs with lymphoma before any treatment and in dogs that had previously received glucocorticoids. Glucocorticoids are often used by clinicians as first drugs after diagnosis for immediate health improvement and are known to impact monocyte number. We have shown an increase in the percentage of MHCII− monocytes, regardless of treatment. However, only in dogs that had received glucocorticoids were changes in the proportion of MHCII+ and MHCII− monocytes reflected also by the changes in the number of MHCII− monocytes in the blood, which was significantly higher. Evaluating the changes in canine monocytes might be helpful in the diagnosis of various tumor types, monitoring of the treatment or assessing the immune status of dogs. ABSTRACT: An increase in the percentage of monocytes with reduced HLA-DR expression and immunosuppressive properties has been reported in numerous human neoplastic diseases, including lymphoma. However, there are no analogous studies on phenotypical variations in the peripheral blood monocytes in dogs with lymphoma. The aim of this study was to determine the difference in the expression of the MHCII molecule on peripheral blood monocytes in dogs with lymphoma before any treatment (NRG) and in dogs that had previously received glucocorticoids (RG) in comparison to healthy dogs. Flow cytometry immunophenotyping of peripheral blood leukocytes was performed using canine-specific or cross-reactive antibodies against CD11b, CD14 and MHCII. In the blood of dogs with lymphoma (NRG and RG), compared to that of healthy ones, the MHCII+ and MHCII− monocytes ratio was changed due to an increase in the percentage of MHCII− monocytes. The number of MHCII− monocytes was significantly higher only in RG dogs compared to healthy ones, which might result from the release of these cells from the blood marginal pool due to the action of glucocorticoids. Our results encourage further studies to assess if changes in MHCII expression affect immune status in dogs with lymphoma.