EFFECT OF SELECTION OF SWINE FOR HIGH AND LOW IMMUNE RESPONSIVENESS ON MONOCYTE SUPEROXIDE ANION PRODUCTION AND CLASS-II MHC ANTIGEN EXPRESSION

Monocyte function was investigated in second (G2) and third (G3) gener ation pigs selected for high and low antibody and cell-mediated immune responsiveness. In groups of pigs from the high- and low-immune respo nse lines, monocyte release of superoxide anion (O2-) was assayed in r esponse to phorbol 12-myristate-13-acetate and expression of the Class II MHC (MHC-II) antigens SLA-DR and SLA-DQ, determined using flow cyt ometry. Analysis of variance using a linear model demonstrated no sign ificant intergroup differences in O2- production by lymphokine-activat ed monocytes from G2 pigs. In G3 pigs, there were no significant inter group differences in the percentage of MHC-II+ cells or in the density of expression of either SLA-DR or SLA-DQ. In individual pigs, monocyt e SLA-DR and SLA-DQ expression was similar in terms of the percentage of MHC-II+ cells and in the magnitude of MHC-II expression. Litter con tributed significantly to variation in monocyte O2- production in G2 p igs (P less-than-or-equal-to 0.005) and SLA-DQ (P less-than-or-equal-t o 0.01) expression. Although the lines differed significantly in corre lates of antibody and cell-mediated immune response, there was no appa rent effect of selection for high and low immune responsiveness in swi ne on monocyte O2- production and MHC-II expression.