Internal defence mechanisms in Patella

Abstract

The haemocytes of Patella were examined living and fixed and stained, by light microscopy and scanning electron microscopy. Similarities between haemocytes and vertebrate macrophages are probably a result of their similar functions, not of homology.

The activity of the haemolymph was examined and found to contain no lytic factors or agglutinins to vertebrate red cells or to bacteria. A haemagglutinin-inhibition factor was found to be present, this inhibited the agglutination of human red blood cells (HRBC) by human anti-sera, but not that of sheep red cells by guinea-pig anti-sheep serum.

Cultured in vitro, the haemocytes were found to lyse HRBC. This was quantified and found to be unaffected by prior opsonisation of the HRBC in Patella haemolymph. The haemocytes of pre-injected animals were found to be more avid. The haemocytes were able to phagocytose bacteria, when cultured with them in vitro. Opsonisation in haemolymph depressed bacterial uptake, but the haemolymph of pre-injected animals slightly enhanced uptake.

Acid phosphatase was found to be naturally present in the haemocytes and haemolymph. Injection with bacteria resulted in elevated acid phosphatase levels and haemocyte numbers. Sea water injection did not cause elevation of haemocyte acid phosphatase or haemocyte number. Enhanced lysin synthesis is possibly a response to the foreign particles. Culture of haemocytes in vitro with bacteria did not cause detectable changes of acid phosphatase in the culture medium, although cellular levels changed. It is suggested that the haemocytes are not the primary source of this enzyme in the haemolymph. Since the haemolymph is not bactericidal it is suggested that haemolymph lysins may have an opsonic function.

The results are discussed with reference to similar work which has been done on other molluscs.