We report here that human B cells produce thymus and activation-regulated chemokine (TARC/CCL17) and macrophage derived chemokine (MDC/CCL22) if stimulated with anti-CD40 and IL-4. The production was determined by both protein and mRNA level using specific ELISA and semi-quantitative RT-PCR methods. Since the ligand of the TARC and MDC is CCR4, which is specifically expressed on Th2 type T cells, the production of these CC chemokines is likely to play important roles in the T cell and B cell interaction. Consistent with this, ovalbumin (OVA) specific IgE levels, which reflect the T-B cell interaction, are significantly correlated with the amounts of TARC and MDC in sera. Furthermore, we found that TARC and MDC levels are significantly increased in the sera obtained from patients with atopic dermatitis, and that the amounts are correlated with the severity of atopic dermatitis. Since CD40 ligand and IL-4 are produced by activated T helper cells, these results indicate that TARC and MDC produced by B cells play important roles in the production of antigen specific IgE by the T-B cell interaction and in the pathogenesis of allergic disease.