Regulation of self-tolerance by Qa-1-restricted CD8(+) regulatory T cells

Mounting an efficient immune response to pathogens while avoiding damage to host tissues is the central task of the immune system. Emerging evidence has highlighted the contribution of the CD8⁺ lineage of regulatory T cells to the maintenance of self-tolerance. Specific recognition of the MHC class Ib molecule Qa-1 complexed to peptides expressed by activated CD4⁺ T cells by regulatory CD8⁺ T cells triggers an inhibitory interaction that prevents autoimmune responses. Conversely, defective Qa-1-restricted CD8⁺ regulatory activity can result in development of systemic autoimmune disease. Here, we review recent research into the cellular and molecular basis of these regulatory T cells, their mechanism of suppressive activity and the potential application of these insights into new treatments for autoimmune disease and cancer.     

Colostral antibody-mediated and cell-mediated immunity contributes to innate and antigen-specific immunity in piglets

Immunoglobulins and immune cells are critical components of colostral immunity; however, their transfer to and function in the neonate, especially maternal lymphocytes, is unclear. Cell-mediated and antibody-mediated immunity in sow blood and colostrum and piglet blood before (PS) and after (AS) suckling were assessed to investigate transfer and function of maternal immunity in the piglet. CD4, CD8, and γδ lymphocytes were found in sow blood and colostrum and piglet blood PS and AS; each had a unique T lymphocyte profile. Immunoglobulins were detected in sow blood, colostrum, and in piglet blood AS; the immunoglobulin profile of piglet serum AS mimicked that of sow serum. These results suggest selectivity in lymphocyte concentration into colostrum and subsequent lymphocyte transfer into the neonate, but that immunoglobulin transfer is unimpeded. Assessment of colostral natural killer activity and antigen-specific proliferation revealed that colostral cells are capable of influencing the innate and specific immune response of neonatal pigs.     

Activation requirements and responses to TLR ligands in human CD4 T cells: Comparison of two T cell isolation techniques

Direct regulation of T cell function by microbial ligands through Toll-like receptors (TLR) is an emerging area of T cell biology. Currently either immunomagnetic cell sorting (IMACS) or fluorescence-activated cell sorting (FACS), are utilized to isolate T-cell subsets for such studies. However, it is unknown to what extent differences in T cell purity between these isolation techniques influence T cell functional assays. We compared the purity, response to mitogen, activation requirements, and response to TLR ligands between human CD4⁺ T cells isolated either by IMACS (IMACS-CD4⁺) or by IMACS followed by FACS (IMACS/FACS-CD4⁺). As expected, IMACS-CD4⁺ were less pure than IMACS/FACS-CD4⁺ (92.5% ± 1.4% versus 99.7% ± 0.2%, respectively). Consequently, IMACS-CD4⁺ proliferated and produced cytokines in response to mitogen alone and had lower activation requirements compared to IMACS/FACS-CD4⁺. In addition IMACS-CD4⁺ but not IMACS/FACS-CD4⁺ responses were upregulated by the TLR-4 ligand lipopolysaccharide (LPS). On the other hand, TLR-2 and TLR-5 engagement induced costimulation in both IMACS-CD4⁺ and highly purified IMACS-/FACS-CD4⁺. Altogether these results indicate that small differences in cell purity can significantly alter T cell responses to TLR ligands. This study stresses the importance of a stringent purification method when investigating the role of microbial ligands in T cell function.     

Use of HLA-DR*08032/E7 and HLA-DR*0818/E7 tetramers in tracking of epitope-specific CD4+ T cells in active and convalescent tuberculosis patients compared with control donors

Comparative tracking of tetramer-positive and epitope-specific CD4⁺ T cells in blood and other tissues from tuberculosis (TB) patients during TB development and treatment using control donor samples is not well characterized. In this study, a novel HLA-DR-restricted peptide E7 from the ESAT-6 protein of Mycobacterium tuberculosis (MTB) was used to prepare modified HLA-DR*08032/E7 tetramer (tetramer 1) and HLA-DR*0818/E7 tetramer (tetramer 2) to monitor a series of samples from TB patients and control donors. Tetramer staining showed that (1) by direct staining of single sample and flow cytometric analyses, detection of tetramer-positive CD4⁺ T cells ranged from 0.1% to 8.8% (median 0.67% in tetramer 1 and 0.5% in tetramer 2), 0.1 to 10.7% (0.74% and 0.71%), 0.02 to 2.2% (0.25% and 0.25%), 0.02 to 0.48% (0.2% and 0.2%) and most at under 0-0.2% (0.2% and 0.16%) in the initial pulmonary TB (PTB) patients’ blood, pleural fluid (PLF) of initial tuberculous pleuritis patients, non-TB patients’ blood, healthy donors’ blood and umbilical cord blood, respectively; significantly higher levels of CD4⁺ T cells were detected in samples of TB patients than in three control donor groups; (2) by direct staining of time point TB samples and flow cytometric analyses, along with TB symptom amendment at day 60, tetramer-positive CD4⁺ T cells began to decrease, until after 90-120 days, reached and kept at a relatively low even normal level about at 0.03-0.3%; (3) by enrichment approach, at least 10-fold increased memory tetramer-positive CD4⁺ T cells were seen; (4) by in situ staining, tetramer-positive, IFN-γ-producing and/or TNF-α-producing CD4⁺ T cells in the lymph node and lung granuloma and cavernous tissues of TB patients could be determined. Therefore, by further increasing the sample size tested to confirm the specificity and sensitivity of tetrameric molecules, it should be possible to develop them for use as research and diagnostic reagents.