Comparative phagocytic and pinocytic activities of leucocytes from peripheral blood and lymphomyeloid tissues of the nurse shark (Ginglymostoma cirratumBonaterre) and the clearnose skate (Raja eglanteriaBosc)

Cells isolated from lymphomyeloid tissues and peripheral blood from two species of elasmobranch, the nurse shark (Ginglymostoma cirratumBonaterre) and the clearnose skate (Raja eglanteriaBosc) were assayed forin vitrophagocytic and pinocytic activities at various times during 24 h in culture. The purpose of this research was to begin to characterise functional activities of cells isolated from unique lymphomyeloid tissues found in elasmobranchs. Phagocytosis was evaluated by assessing relative abilities of immune cells to ingest Congo Red stained yeast, and included determination of percentage of active cells and numbers of yeast per cell. Pinocytosis was assayed by spectrophotometric measurement of neutral red dye accumulation by immune cells. Phagocytic activity was greatest in cells isolated from shark epigonal and skate epigonal and Leydig organs, with over 60% of skate Leydig cells containing yeast after 24 h in culture. Phagocytic activity was 2·5–6 times lower in cells from peripheral circulation or spleen. Pinocytosis was 1·5–3-fold greater in cells isolated from Leydig and epigonal organs compared to peripheral blood leucocytes or splenocytes. Documentation of phagocytic and pinocytic activities by cells isolated from epigonal and Leydig organs suggests significant immune functional roles for these unique tissues in the elasmobranch immune system.