Effects of salivary gland extract (SGE) from Rhipicephalus sanguineus on immunoglobulin class productivity of canine peripheral blood lymphocytes (PBL) in vitro were studied. The detectable limit of the ELISA for canine total immunoglobulin, IgM and A was at least 1, 1 and 15 ng/ml, respectively, and it seems to be useful for the evaluation of non-specific immunoglobulin class productivity in vitro. SGE from R. sanguineus suppressed pokeweed mitogen- or lipopolysaccharide-induced total immunoglobulin and IgA productivity of canine PBL although IgM productivity was not suppressed. These results suggested that the suppression was caused partly by the direct effect of SGE on B lymphocytes.