The present invention addresses the problem of providing a novel medical agent for prevention of auto-immune diseases, inhibition of symptom progression thereof, inhibition of recurrence thereof, or treatment thereof. As a result of conducting extensive studies, the inventors of the present invention have focused attention on PD-1/CD19 bispecific antibody as a substance with the potentiality of solving the problem, and have achieved the present invention. The PD-1/CD19 bispecific antibody according to the present invention exhibits growth-inhibitory action and immunoglobulin production inhibitory action against activated B cells, and also has inhibitory action against production of cytokine from memory T cells.