Abstract:Canine pregnant sera were investigated for monocyte‐specific cytotoxic antibodies against a cell panel from 50 unrelated dogs. Contaminating DLA and DLB reactivity was removed by absorption on a random pool of purified lymphocytes. Two monocyte‐associated antigens were recognized by two independent clusters of antisera; the existence of further antigens is suggested. In preliminary segregation studies, the inheritance of these determinants in linkage with DLA could not be obser