Preparations of anti-DNA sIgA were obtained from human milk by sequential chromatography on protein A-sepharose, DEAE-fractogel and DNA-cellulose. The influence of oligonucleotides on protein kinase activity was investigated. It was discovered that incubation of anti-DNA sIgA with oligodeoxyriboadenylate d(A)12 stimulates the phosphorylation of polypeptides of sIgA in the presence of [gamma-32P]ATP. The greatest was the incorporation of P into the sIgA H-chains. We also demonstrated stimulation of the casein kinase activity of anti-DNA sIgA by d(A)12. The stimulation of the protein kinase activity of anti-DNA sIgA by oligoriboadenylate r(A)12 was not detected.