CROSS-REACTIVITY OF ANTI-YELLOWTAIL THYMIC LYMPHOCYTE MONOCLONAL-ANTIBODY (YET-2) WITH LYMPHOCYTES FROM OTHER FISH SPECIES

The monoclonal antibody YeT-2, generated in mice hyper-immunized with thymic lymphocytes of the yellowtail, Seriola quinqueradiata, reacts w ith the major population of peripheral blood lymphocytes, which might be putative T cells. In this study, we examined the cross-reactivity o f YeT-2 with lymphocytes from various fish species. Flow cytometric an alysis 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 h ead-kidney. Among the six fish species examined, only the red sea brea m, 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 periphe ral blood of the red sea bream were lymphocytes or unidentified leueoc ytes. Thymic lymphocytes of the red sea bream were also immunocytochem ically stained with YeT-2. The molecular weight of the YeT-2 cross-rea cting antigen on blood cells from the red sea bream was identical with that from the yellowtail, which was identified at approximately 115 k Da. These results suggest that the monoclonal antibody YeT-2 recognize s a conserved antigen on lymphocytes common to the red sea bream and y ellowtail.