gammadelta T cells: the overlooked T-cell subset in demyelinating disease

B7-H3 confers resistance to Vγ9Vδ2 T cell-mediated cytotoxicity in human colon cancer cells via the STAT3/ULBP2 axis

Immunotherapy based on γδT cells has limited efficiency in solid tumors, including colon cancer (CC). The immune evasion of tumor cells may be the main cause of the difficulties of γδT cell-based treatment. In the present study, we explored whether and how B7-H3 regulates the resistance of CC cells to the cytotoxicity of Vγ9Vδ2 (Vδ2) T cells. We observed that B7-H3 overexpression promoted, while B7-H3 knockdown inhibited, CC cell resistance to the killing effect of Vδ2 T cells in vitro and in vivo. Mechanistically, we showed that B7-H3-mediated CC cell resistance to the cytotoxicity of Vδ2 T cells involved a molecular pathway comprising STAT3 activation and decreased ULBP2 expression. ULBP2 blockade or knockdown abolished the B7-H3 silencing-induced increase in the cytotoxicity of Vδ2 T cells to CC cells. Furthermore, cryptotanshinone, a STAT3 phosphorylation inhibitor, reversed the B7-H3 overexpression-induced decrease in ULBP2 expression and attenuated the killing effect of Vδ2 T cells on CC cells. Moreover, there was a negative correlation between the expression of B7-H3 and ULBP2 in the tumor tissues of CC patients. Our results suggest that the B7-H3-mediated STAT3/ULBP2 axis may be a potential candidate target for improving the efficiency of γδT cell-based immunotherapy in CC.

γδ T Cells Coexpressing Gut Homing α4β7 and αE Integrins Define a Novel Subset Promoting Intestinal Inflammation

γδ T lymphocytes, dominant T cell subsets in the intestine, mediate both regulatory and pathogenic roles, yet the mechanisms underlying such opposing effects remain unclear. In this study, we identified a unique γδ T cell subset that coexpresses high levels of gut-homing integrins, CD103 and α4β7. They were exclusively found in the mesenteric lymph node after T cell-mediated colitis induction, and their appearance preceded the inflammation. Adoptive transfer of the CD103⁺α4β7^high subsets enhanced Th1/Th17 T cell generation and accumulation in the intestine, and the disease severity. The level of generation correlated with the disease severity. Moreover, these cells were also found to be elevated in a spontaneous mouse model of ileitis. Based on the procolitogenic function, we referred to this subset as "inflammatory" γδ T cells. Targeting inflammatory γδ T cells may open a novel strategy to treat inflammatory diseases where γδ T cells play a pathogenic role including inflammatory bowel disease.

The good and the bad of neuroinflammation in multiple sclerosis

Multiple sclerosis (MS) is the most common inflammatory, demyelinating, neurodegenerative disorder of the central nervous system (CNS). It is widely considered a T-cell mediated autoimmune disease that develops in genetically susceptible individuals, possibly under the influence of certain environmental trigger factors. The invasion of autoreactive CD4+ T-cells into the CNS is thought to be a central step that initiates the disease. Several other cell types, including CD8+ T-cells, B-cells and phagocytes appear to be involved in causing inflammation and eventually neurodegeneration. But inflammation is not entirely deleterious in MS. Evidence has accumulated in the recent years that show the importance of regulatory immune mechanisms which restrain tissue damage and initiate regeneration. More insight into the beneficial aspects of neuroinflammation might allow us to develop new treatment strategies for this enigmatic disease.

Downregulation of CD94/NKG2A inhibitory receptor on decreased γδ T cells in patients with systemic lupus erythematosus

γδ T cells are characterized by recognizing conserved endogenous and stress-induced antigens without antigen presentation. It has been show that γδ T cells play an important role in anti-tumour/microbe responses, but their function in autoimmune diseases is yet not clear. Here, we reported the quantity and phenotype of peripheral blood γδ T cells from systemic lupus erythematosus (SLE). Both the percentages of γδ T cells in peripheral blood and among CD3(+) T cells of patients with SLE were significantly decreased, regardless of disease activity. However, activating marker CD69 and HLA-DR was upregulated, while inhibiting receptor CD94/NKG2A was downregulated in γδ T cells of patients with SLE. The expression of CD69 is negatively correlated with the quantity of γδ T cells. Moreover, the expression of CD94/NKG2A remained low even with antigen stimulation on those γδ T cells. Our results suggested that the low expression level of CD94/NKG2A upon γδ T cell activation might lead to the over-activation of γδ T cells in patients with SLE. These findings will be useful in elucidating the roles of γδ T cells in SLE pathogenesis.

Change of γδTCR-Expressing T Cells in Healthy Aging

A mature T-cell lineage with the capacity to proliferate in response to receptor-mediated signals and to display non-major histocompatibility complex (MHC)-restricted cytolysis expresses a CD3-associated heterodimer made up of the protein encoded by the T-cell receptor (TCR) gamma-gene. We investigated the possible differences in lymphocyte subpopulations between healthy young-middle-aged and elderly subjects, focusing attention on y8-TCR-expressing cells. The study was carried out on fifteen healthy young-middle-aged male subjects (age range 36–55 years) and fifteen healthy elderly male subjects (age range 67–79 years). Lymphocyte subpopulations were analyzed in blood samples collected every four hours for 24 hours. The presence of circadian rhythmicity on absolute counts was validated to evaluate the periodicity of variation, and the fractional variation between single time point values was calculated to evaluate the dynamics of variation. In the group of young and middle-aged subjects a clear circadian rhythm was validated for the time-qualified changes of all the lymphocyte subpopulations (CD3, CD4, CD4/CD8 ratio, CD20, CD25 and HLA-DR with acrophase at night, CD8, CD16 and TcRγδ with acrophase at noon). In the group of elderly subjects a clear circadian rhythm was validated for the nyctohemeral changes of CD3, CD8, CD4/CD8 ratio, CD 16, CD25. There was a statistically significant difference for the Midline Estimating Statistic of Rhythm (MESOR) of CD3 (p=0.001), CD25 (p=0.003) and γδ-TCR- expressing cells (p=0.004), higher in the elderly, and for the MESOR of HLA-DR (p=0.002) and CD20 (p=0.002) higher in the young and middle-aged subjects. There was a statistically significant difference between the groups in the fractional variation of TcRγδ-expressing cells between 18:00h and 22:00h values (higher in elderly subjects, p=0.007). In conclusion, specific lymphocyte subsets present different levels and different profiles of nyctohemeral changes in healthy young-middle aged in respect to elderly subjects, since B cells are decreased, whereas CD25 and γδ-TCR-bearing cells are higher in the elderly, but the rhythm and the dynamics of variation of this lymphocyte subset is severely altered and this phenomenon might contribute to the onset of age-related variations of the immune responses.