Oral administration of aqueous extract of Carthami Flos induces macrophage activation and preferentially potentiates type 1 helper T-cell response in vivo.

In vivo immunomodulatory activity of aqueous extract of Carthami Flos (AECF) was investigated using a mouse model immunized with keyhole limpet hemocyanin. Serum level of Ag-specific IgG2a was significantly elevated by oral administration of AECF but not IgG1. However, no selective B-cell proliferation by AECF was observed in vivo. Ag-specific proliferation and IFN-gamma and IL-5 production of draining lymph node T cells also was higher in AECF-treated mice when compared with water-treated control mice. However, AECF failed to enhance nonspecific T-cell response under CD3 stimulation. These results led us to hypothesize that AECF potentiates Ag-specific T-cell response, possibly through activation of antigen presenting cells (APC) other than B cells. Functional assessment of splenic macrophages showed that AECF administration significantly enhances IL-12 production as well as APC activity for IFN-gamma production and STAT-4 activation by T cells. Collectively, these data strongly support that AECF preferentially potentiates immune response polarized toward TH1 and for which increased activation of macrophages is most likely to be responsible. The present data implicate a possible application of AECF to potentiate cellular immunity and, we hope, prevent intracellular infections.

Committed memory effector type 2 cytotoxic T (Tc2) cells are ineffective in protective anti-tumor immunity.

Cytotoxic CD8+ T cells (Tc) are a major effector cell population in protection against tumor growth and classified into Tc1 or Tc2 based on their cytokine-secreting profiles. However, their relative tumor protective roles remain undefined. In the present study, CD8+ memory T cells were obtained from mice given with CT26-IL 12 and tumor-specific Tc1 and Tc2 cells were induced by in vitro primary stimulation (1 degrees). In vivo anti-tumor immunity and in vitro cytotoxicity of 1 degrees Tc2 memory effector cells were highly protective comparably to 1 degrees Tc1, but they secreted high level of IFNgamma as well as IL 4 and IL 5. Moreover, memory cells obtained again from tumor-protected mice by either 1 degrees Tc1 or Tc2 transfer showed indistinguishable, Tc1-like, cytokine profiles. These results strongly suggest that 1 degrees Tc2 cells are insufficiently polarized. Tc2 memory effector cells were therefore examined for their transitional anti-tumor activity during consecutive stimulation until Th2 commitment. Secondary stimulation (2 degrees) markedly reduced secretion of IFNgamma (by 94%) and in vivo tumor protection (by 83%). Tertiary (3 degrees) and further stimulation completely abrogated both of tumor protective activity and IFNgamma secretion of Tc2 cells. This progressive loss of activity following repeated stimulation was accompanied by a reduction of in vitro cytotoxicity to CT26 tumor cells. In addition, when 1 degrees Tc2 cells were trans-differentiated to Tc1 during secondary stimulation, 2 of 6 cultures recovered tumor protective activity concomitantly with IFNgamma secretion, indicating that repeated stimulation does not deteriorate tumor protective activity of 2 degrees Tc2 cells. Collectively, these data demonstrate that highly committed Tc2 cells are ineffective in tumor protection.

In vitro immunomodulatory activity of Bo-yang-hwan-o-tang.

Bo-yang-hwan-o-tang (BHT), an herbal decoction has been mainly used for improvement of blood flow in oriental medicine. Its in vivo immunomodulation was recently demonstrated but the effective mechanisms have not been described. This study was carried out to evaluate in vitro immunomodulatory activity of BHT. Water extract of BHT significantly promoted in vitro proliferative responses of mouse spleen cells (SPC) and also further enhanced the proliferation of SPC stimulated with anti-CD3 antibody. Unexpectedly, addition of BHT extract did not affect proliferation of both resting and CD3-activated T cells, whereas it showed a strong mitogenic activity on B cells. Flow cytometric analysis of CFSE-stained SPC showed that BHT-mediated enhancement of CD3-activated SPC proliferation is due to T cell, but not B cell, division. Mixed culture experiment combining T and mitomycin C-treated B cells demonstrated that BHT-mediated enhancement of CD3-activated T cell proliferation was dependent on the presence of B cells. However, B cell-derived factors were not involved in BHT effect on T cell proliferation. In the presence of B cells, BHT treatment resulted in a great enhancement in IL-2 production of CD3-activated T cells, and BHT effect on T cell proliferation was completely abrogated by addition of exogenous IL-2, indicating that IL-2 plays a critical role in BHT-mediated enhancement of CD3-activated T cell proliferation. Taken together, our data revealed that BHT possesses a potent B cell mitogenic activity and also can enhance activated T cell response through B cell regulation.