Abstract
The monoclonal antibody YeT-2, generated in mice hyper-immunized with thymic lymphocytes of the yellowtail, Seriola quinqueradiata, reacts with the major population of peripheral blood lymphocytes, which might be putative T cells. In this study, we examined the cross-reactivity of YeT-2 with lymphocytes from various fish species. Flow cytometric analysis showed that YeT-2 reacts with 69.8% lymphocytes in the thymus, 89.7% in the peripheral blood, 87.5% in the spleen, and 59.7% in the head-kidney. Among the six fish species examined, only the red sea bream, Pagrus major, which is included in the same suborder Percoidei with the yellowtail, showed the presence of YeT-2 positive cells. Electron microscopic studies revealed that YeT-2 positive cells in the peripheral blood of the red sea bream were lymphocytes or unidentified leucocytes. Thymic lymphocytes of the red sea bream were also immunocytochemically stained with YeT-2. The molecular weight of the YeT-2 cross-reacting antigen on blood cells from the red sea bream was identical with that from the yellowtail, which was identified at approximately 115 kDa. These results suggest that the monoclonal antibody YeT-2 recognizes a conserved antigen on lymphocytes common to the red sea bream and yellowtail.
