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) generation pigs selected for high and low antibody and cell-mediated immune responsiveness. In groups of pigs from the high-and low-immune response lines, monocyte release of superoxide anion (O2-) was assayed in response to phorbol 12-myristate-13-acetate and expression of the Class II-MHC (MHC-II) antigens SLA-DR and SLA-DQ, determined using flow cytometry. Analysis of variance using a linear model demonstrated no significant intergroup differences in O2- production by lymphokine-activated monocytes from G2 pigs. In G3 pigs, there were no significant intergroup differences in the percentage of MHC-II+ cells or in the density of expression of either SLA-DR or SLA-DQ. In individual pigs, monocyte 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 contributed significantly to variation in monocyte O2- production in G2 pigs (P < or = 0.005) and SLA-DQ (P < or = 0.01) expression. Although the lines differed significantly in correlates of antibody and cell-mediated immune response, there was no apparent effect of selection for high and low immune responsiveness in swine on monocyte O2- production and MHC-II expression.