Downregulation of CD4+CD25+ regulatory T cells may underlie enhanced Th1 immunity caused by immunization with activated autologous T cells

Regulatory T cells （Treg） play important roles in immune system homeostasis, and may also be involved in tumor immunotolerance by suppressing Th1 immune response which is involved in anti-tumor immunity. We have previously reported that immunization with attenuated activated autologous T cells leads to enhanced anti-tumor immunity and upregulated Thl responses in vivo. However, the underlying molecular mechanisms are not well understood. Here we show that Treg function was significantly downregulated in mice that received immunization of attenuated activated autologous T cells. We found that Foxp3 expression decreased in CD4＋CD25＋ T cells from the immunized mice. Moreover, CD4＋CD25＋Foxp3＋ Treg obtained from immunized mice exhibited diminished immunosuppression ability compared to those from naive mice. Further analysis showed that the serum of immunized mice contains a high level ofanti-CD25 antibody （about 30 ng/ml, p〈0.01 vs controls）. Consistent with a role ofanti-CD25 response in the downregulation of Treg, adoptive transfer of serum from immunized mice to naive mice led to a significant decrease in Treg population and function in recipient mice. The triggering of anti-CD25 response in immunized mice can be explained by the fact that CD25 was induced to a high level in the ConA activated autologous T cells used for immunization. Our results demonstrate for the first time that immunization with attenuated activated autologous T cells evokes anti-CD25 antibody production, which leads to impeded CD4＋CD25＋Foxp3＋ Treg expansion and function in vivo. We suggest that dampened Treg function likely contributes to enhanced Thl response in immunized mice and is at least part of the mechanism underlying the boosted anti-tumor immunity.

Impact of the microenvironment on the pathogenesis of mucosaassociated lymphoid tissue lymphomas

Approximately 8%of all non-Hodgkin lymphomas are extranodal marginal zone B cell lymphomas of mucosa-associated lymphoid tissue(MALT),also known as MALT lymphomas.These arise at a wide range of different extranodal sites,with most cases affecting the stomach,the lung,the ocular adnexa and the thyroid.The small intestine is involved in a lower percentage of cases.Lymphoma growth in the early stages is associated with long-lasting chronic inflammation provoked by bacterial infections(e.g.,Helicobacter pylori or Chlamydia psittaci infections)or autoimmune conditions(e.g.,Sjögren’s syndrome or Hashimoto thyroiditis).While these inflammatory processes trigger lymphoma cell proliferation and/or survival,they also shape the microenvironment.Thus,activated immune cells are actively recruited to the lymphoma,resulting in either direct lymphoma cell stimulation via surface receptor interactions and/or indirect lymphoma cell stimulation via secretion of soluble factors like cytokines.In addition,chronic inflammatory conditions cause the acquisition of genetic alterations resulting in autonomous lymphoma cell growth.Recently,novel agents targeting the microenvironment have been developed and clinically tested in MALT lymphomas as well as other lymphoid malignancies.In this review,we aim to describe the composition of the microenvironment of MALT lymphoma,the interaction of activated immune cells with lymphoma cells and novel therapeutic approaches in MALT lymphomas using immunomodulatory and/or microenvironmenttargeting agents.