Ability of the polysaccharide chitosan to inhibit proliferation of CD4+lymphocytes from mucosal inductive sites, in vitro and in vivo

Objective: After oral administration of chitosan (a copolymer of glucosamine and N-acetylglucosamine), mesenteric lymph node (MLN) lymphocytes exhibited traits of anergy, a process coupled with inability of mature T cells to proliferate. We wondered whether biological activity of chitosan could be affecting division of lymphocytes at the mucosal inductive sites. Materials and methods: We studied the effect of chitosan on proliferation of carboxyfluorescein diacetate-labelled MLN lymphocytes stimulated with concanavalin A in vitro. We assessed expression of CD25 and CD71 activation markers and pro-apoptotic molecule CD95L. Moreover, we studied the effect of chitosan ex vivo, in carboxyfluorescein diacetate-labelled MLN cells isolated after feeding single or repetitive doses of the polysaccharide, and we evaluated cell cycle parameters. Results: Chitosan suppressed cell proliferation and down-modulated expression of CD25 in these MLN CD4+ cells isolated from normal rats. After in vivo contact, chitosan inhibited proliferation of MLN cells and reduced secretion of interferon-gamma. Furthermore, sustained feeding produced reduction in percentage of CD4+ cells in S phase of the cell cycle. Conclusion: Here we demonstrate the ability of chitosan to suppress proliferation of CD4+ lymphocytes from mucosal inductive sites in vivo and in vitro This effect could be relevant in modulatory activity of chitosan in the intestinal microenvironment.