THE PLASMA-LEVELS OF CONGLUTININ ARE HERITABLE IN CATTLE AND LOW-LEVELS PREDISPOSE TO INFECTION

Conglutinin, like mannan-binding lectin (MBL) and CL-43, is a serum co llectin involved in the innate immune defence system. In man, low seru m MBL concentrations. resulting from mutations in the collagen region, are associated with a common opsonic defect. Plasma levels of conglut inin in cattle were assayed by rocket immunoelectrophoresis to examine whether they were genetically determined. Samples were collected from calves (309 bull-calves and 260 heifers with complex pedigree relatio nships). The number of respiratory infections from the 42nd to 336th d ay of life was recorded. The number of infections was found to be gene tically determined (heritability: h(2) = 0.31+/-0.07). A wide concentr ation range of conglutinin was found in plasma (<1.25-35 mu g/ml for f emales, geometric mean 8.1 mu g/ml, and <1.25-47 mu g/ml for males, ge ometric mean 15.5 mu g/ml), and the concentration was found to be gene tically determined (heritability, h(2)= 0.52+/-0.07). The analysis rev ealed a negative association between disease frequency and the conglut inin levels (-0.56+/-0.18 for female: -050+/-0.18 for male). Levels of conglutinin below the detection limit of the assay (1.25 mu g/ml) wer e found in 2% of the animals. If these animals are assumed to be homoz ygous for a single recessive allele causing low concentrations a gene frequency of 0.15 could be calculated. These findings suggests that se lection for resistance against infectious disease is possible in cattl e and that the level of plasma conglutinin may be a helpful trait in s uch a breeding scheme.