Altered antibody production and helper T cell function in mice lacking chemokines CCL19 and CCL21-Ser.

The roles of chemokines CCL19 and CCL21 in Ab production were investigated using plt mutant mice, which lack expression of CCL19 and CCL21-ser in their lymphoid organs. In these mice, the Th response has been shown to tend towards the Th1 type because of accumulation of inflammatory dendritic cells. When plt mice were immunized with 100 µg OVA in CFA, the number of Ab-forming cells in the draining LN, and serum concentrations of OVA-specific IgM and IgG Ab, were very close to those of the control, yet IgG2a Ab in plt mice was increased. In vitro IFN-γ production by the draining LN cells of plt mice was increased. In addition, the ability of helper T cells from plt mice to stimulate Ab production in vitro was prolonged. Also, in the plt mice, in vivo challenge with OVA in incomplete Freund's adjuvant elicited a stronger IgG2a response and a weaker IgG1 response, which is suggestive of a Th1-dominant response. Similar findings were obtained when mice were immunized with 100 µg OVA in alum, except that with alum the increases observed in plt mice were IgG1 produced in vivo and IL-4 produced in vitro by draining LN cells. Furthermore, immunization with alum adjuvant also induced a prolonged in vitro recall response of IFN-γ and IL-4. These findings indicate that plt mice mount an anti-OVA Ab response, and suggest that CCL19 and CCL21 induce prompt Ab responses to antigen, and negatively regulate helper T cell responses in vivo.