MR1-restricted Vα19i T cells - a second population recognizing lipid antigens?

Regulatory B cells in autoimmune diseases and mucosal immune homeostasis

B lymphocytes contribute to physiological immunity through organogenesis of secondary lymphoid organs, presentation of antigen to T cells, production of antibodies, and secretion of cytokines. Their role in several autoimmune diseases, mainly as producers of pathogenic antibodies, is also well known. However, certain subsets of B cells are emerging as the important regulatory cell populations in both mouse and human. The regulatory functions of B cells have been demonstrated in a variety of mouse models of autoimmune diseases including collagen-induced arthritis (CIA), experiment autoimmune encephalomyelitis (EAE), anterior chamber-associated immune deviation (ACAID), diabetes, contact hypersensitivity (CHS), and intestinal mucosal inflammation. Accumulating evidence from both mouse and human studies confirms the existence of regulatory B cells, and is beginning to define their mechanisms of action. In this article, we first review the history of B cells with regulatory function in autoimmune diseases, and summarize the current understanding about the characterizations of such B-cell subsets. We then discuss the possible regulatory mechanisms of B cells, and specifically define the role of regulatory B cells in immune homeostasis in the intestine.

Invariant Valpha7.2-Jalpha33 TCR is expressed in human kidney and brain tumors indicating infiltration by mucosal-associated invariant T (MAIT) cells

The anti-tumor response of human invariant NKT (NKT) cells is well established. A novel T cell subset, mucosal-associated invariant T (MAIT) cells, possesses similar regulatory properties to NKT cells in autoimmune models and disease. Here, we examined the clonality of four T cell subsets expressing invariant alphaTCR, including Valpha7.2-Jalpha33 of MAIT cells, in 19 kidney and brain tumors. The MAIT clonotype was identified and co-expressed with NKT clonotype in half of the tumors. In contrast, two other invariant T cell clonotypes (Valpha4 and Valpha19) were not present in tumors. Such tumors also expressed Vbeta2 and Vbeta13, the restricted TCRbeta chain of MAIT cells and the antigen-presenting molecule MR1. A high percentage of infiltrating T cells was CD8+ and expressed HLA-DR suggesting activation. Although the MAIT alphaTCR was identified in both peripheral CD56+ and CD56- subsets, infiltrating lymphocytes were CD56 negative. The clonal presence of MAIT cells in tumors correlated with the expression of pro-inflammatory cytokines but no IL-4, IL-5 and IL-10, suggesting that a pro-inflammatory subset of human MAIT cells may exist. Our data imply that a CD56- subset of MAIT cells may participate in tumor immune responses similarly to NKT cells.