Macrophages, rather than T and B cells are principal immunostimulatory target cells of Lycium barbarum L. polysaccharide LBPF4-OL

Abstract

Aim of the study: Lycium barbarum L. is a renowned Yin strengthening agent in traditional Chinese medicine. Lycium barbarum L. polysaccharide-protein complex is well-known for its immunoregulatory and antitumor effects. LBPF4-OL is the glycan part of Lycium barbarum L. polysaccharide-protein complex fraction 4 (LBPF4). LBPF4-OL's active contribution in LBPF4 is still blank. In the study, we enrich the polysaccharide part of Lycium barbarum L. polysaccharide-protein complex, and investigate its immunostimulatory effects on mouse spleen cells, T cells, B cells and macrophages.

Materials and methods: Balb/C mice were used in vitro and in vivo studies. In in vitro study, lymphocyte proliferations were analyzed with (3)H-TdR incorporation method. Miltenyi MicroBeads were used in the purification of lymphocytes. Activation of T and B cells was analyzed by flow cytometry. In order to obtain the peritoneal macrophages, mice were injected i.p. with 1mL of sodium thioglycollate 3 days prior to killing. Spleen cells were stimulated with LBPF4-OL and cytokine concentrations in the supernatants were determined by multiplex bead analysis. In in vivo study, mice were injected i.p. with 1 mL of normal saline or 100 μg/mL LBPF4-OL daily for 6 days. Peritoneal macrophage functions were analyzed by enzyme-linked immunosorbent assay and flow cytometry assay.

Results: Spleen cells and lymphocyte proliferation assay indicated that LBPF4-OL markedly induced the spleen cell proliferation, but could not induce proliferation of purified T and B lymphocytes. Further research revealed that B cell proliferation took place in the presence of activated macrophages or LPS. Multiplex bead analysis showed that LBPF4-OL can obviously induce IL-6, IL-8, IL-10 and TNF-α production of the spleen cells in a concentration-dependent manner. Flow cytometric analysis showed that LBPF4-OL (i.p.) prompts CD86 and MHC-II molecules expression on macrophages. ELISA assay showed that LBPF4-OL can greatly strengthen macrophage releasing of TNF-α and IL-1β.

Conclusion: These results suggested that glycan LBPF4-OL plays an important role in the immunopharmacological activity of Lycium barbarum L. polysaccharide-protein complex, and primary mouse macrophages, rather than T and B cells, are the principal target cells of it.