Multiple effects caused by anti-IL-4 mAb inoculation in the thymus and spleen of adult mice.

We investigated the physiological role of IL-4 in the thymus and spleen by administering a neutralizing monoclonal anti-IL-4 antibody (11B11 mAb) into adult mice for 7 or 14 days. After this treatment the thymus decreased in size, this was mainly attributed to a decrease in the CD4+CD8+ subset after 7 days and both the CD4+CD8+ and the CD4+CD8- subsets after 14 days. These data suggest that IL-4 has a role in CD4+CD8+ thymocyte development and can differentially modulate the maturation of CD4+CD8- thymocytes in adult mice. Conversely, anti-IL-4 inoculation induced an increase in spleen size. After 7 days of treatment this enlargement appeared to be due to a increase in number of immature cells, the majority of which were CD4-CD8-alpha beta TCR-B220-slg-Ia-Mac-1-Pgp1 positive. After 14 days, an expanded spleen size was mainly due to inflated numbers of mature CD4+CD8-, B and Mac-1+ cells. In addition, we showed that anti-IL4 mAb in vivo enhanced the CD4-CD8-alpha beta TCRlow subset within the spleen after 7 days which is also observed at 14 days of treatment. Finally, we demonstrated that anti-IL-4 mAb treatment is highly stimulatory for hemopoietic activity in the adult spleen. Taken together, these results support the notion that IL-4 acts in vivo, directly or indirectly, on T cell differentiation in the thymus and T subsets homeostasis as well as on other cell types in the spleen of adult mice.