Snapper (Pagrus auratus) leucocyte proliferation is synergistically enhanced by simultaneous stimulation with LPS and PHA

Important channels of communication between mammalian leucocytes have long been recognised. Here, data are reported that suggest similar integrations may occur between snapper leucocytes upon mitogen stimulation. Cell surface immunoglobulin (IgM) expression was used in conjunction with intracellular fluorescence staining and flow cytometry to differentiate proliferating peripheral blood leucocyte subsets (PBLs). Independent activation using phytohaemagglutinin (PHA) or lipopolysaccharide (LPS) drove both mIg⁻and mIg⁺cells into cycle. It is not known if the proliferation of mIg⁺cells was mediated by a mutually exclusive effect of the mitogen on each cell population, cognate cellular interaction or a soluble growth factor. Simultaneous activation of PBLs with PHA and LPS consistently induced significantly more cells to proliferate than the sum of proliferating cells stimulated solely with PHA or LPS. Together, the results suggest that different leucocyte subsets have the capability to influence their respective responses to mitogenic stimulation. Therefore, like in the mammalian immune system, communication may occur between snapper leucocyte subsets.