OPSONIC EFFECT OF EQUINE PLASMA FROM DIFFERENT DONORS

The ability of equine plasma from different donors to enhance phagocyt ic capacity was assessed in neutrophils obtained from seven foals, age d 7-8 days (Study A), and from seven adult horses (Study B). Neutrophi ls were allowed to phagocytize fluorescent yeast cells opsonized with plasma from one of three donors or with pooled serum, all previously f rozen (-18 degrees C) and thawed. The results were analysed by flow cy tometry. In study A, fresh, autologous foal serum was also used for op sonization, and in study B, heat-inactivated plasma and pooled serum w ere used in addition to untreated samples. The plasma from donor GN in duced a higher number of truly phagocytic neutrophils (mean 78%) than, did plasma from donors GD (68%), OD (66%) and pooled serum (59%) when neutrophils from foals were used (p < 0.05). Similar results were obta ined when adult neutrophils were used. Phagocytosis was markedly reduc ed with beat-inactivated plasma as a result of there being fewer phago cytic neutrophils and less phagocytized material per cell. The opsonic capacities of the autologous foal sera were lower than that of adult donor plasma in six out of seven foals. It is concluded that there is significant individual variation in the opsonic activity amongst plasm a donors with similar serum IgG concentrations, The results were consi stent irrespective of whether neutrophils from adults or foals were us ed. (C) 1997 Elsevier Science B.V.