Rapid advances in neuroendocrine immunology have established the concept of bidirectional communication between the immune and neuroendocrine systems. Capsaicin suppresses the immune function by destroying substance P acting as mediatior of neuroendocrine immune systim.

In this stydy, effect of capsaicin on mature murine lymphocyte functions and lymphoid tissue morphology was examined. Formally, capsaicin showed the strong cytotoxic effect on splenocyte over 10µg/ml concentration in citro. And proliferation and Th1-cytokine expression of splenic cells in mice that received high dose of capsaicin (100µg/mouse) were significantly diminished. However, low dose of capsaicin treatment did not influence these responses in vivo(1 µg/mouse) and in vitro (under 5 µg/ml). And the morphology of spleen and lymph nodes after capsaicin treatment was observed. In the spleen of mice injected with high dose of capsaicin (100, 200µg/mouse), the size of white pulp was significantly decreased and the length of red pulp was increased, Moreover, vascularity index was diminished in a dose dependent manner.

These results implies that immunosuppressive effect of capsaicin is associated with cytotoxic activity on lymphocyte, Th1-cytokine down-regulation and lymphoid tissue abnormalization, and this report is expected to give a hand to the study for the mechanism of action of neurotoxin of the immune system.