Activation of purified human T cells by mitogens: diminished mitogen-induced deoxyribonucleic acid synthesis in human T cells compared with autologous peripheral blood lymphocytes

Silencing of aryl hydrocarbon receptor repressor restrains Th17 cell immunity in autoimmune hepatitis

Th17-cells play a key role in the pathogenesis of autoimmune hepatitis (AIH). Dysregulation of Th17-cells in AIH is linked to defective response to aryl-hydrocarbon-receptor (AhR) activation. AhR modulates adaptive immunity and is regulated by aryl-hydrocarbon-receptor-repressor (AHRR), which inhibits AhR transcriptional activity. In this study, we investigated whether defective Th17-cell response to AhR derives from aberrant AHRR regulation in AIH. Th17-cells, obtained from the peripheral blood of AIH patients (n = 30) and healthy controls (n = 30) were exposed to AhR endogenous ligands, and their response assessed in the absence or presence of AHRR silencing. Therapeutic effects of AHRR blockade were tested in a model of Concanavalin-A (Con-A)-induced liver injury in humanized mice. AHRR was markedly upregulated in AIH Th17-cells, following exposure to l-kynurenine, an AhR endogenous ligand. In patients, silencing of AHRR boosted Th17-cell response to l-kynurenine, as reflected by increased levels of CYP1A1, the main gene controlled by AhR; and decreased IL17A expression. Blockade of AHRR limited the differentiation of naïve CD4-cells into Th17 lymphocytes; and modulated Th17-cell metabolic profile by increasing the levels of uridine via ATP depletion or pyrimidine salvage. Treatment with 2'-deoxy-2'-fluoro-d-arabinonucleic acid (FANA) oligonucleotides to silence human AHRR in vivo, reduced ALT levels, attenuated lymphocyte infiltration on histology, and heightened frequencies of regulatory immune subsets in NOD/scid/gamma mice, reconstituted with human CD4 cells, and exposed to Con-A. In conclusion, blockade of AHRR in AIH restores Th17-cell response to AHR, and limits Th17-cell differentiation through generation of uridine. In vivo, silencing of AHRR attenuates liver damage in NOD/scid/gamma mice. Blockade of AHRR might therefore represent a novel therapeutic strategy to modulate effector Th17-cell immunity and restore homeostasis in AIH.

Amphotericin B modifications of peripheral blood lymphocyte and tonsil lymphocyte responses to concanavalin A

Peripheral blood lymphocytes (PBL) were shown previously to be activated to incorporate 3H-thymidine by concanavalin A (con A). Amphotericin B (Am B) was reported to be both immuno-enhancing and suppressive. We investigated the response of PBL and tonsil lymphocytes (TL) to con A in culture, and the effect of Am B on these responses. PBL were activated by con A as expected, and the magnitude of the response diminished as cell density increased. The responses of PBL usually were significantly enhanced by Am B at 2.5 or 5 micrograms/ml, but 10 micrograms Am B/ml significantly inhibited the con A response. TL had relatively high rates of spontaneous proliferation, but Am B was a potent inhibitor of this. TL responded to con A just as well as PBL, and Am B strongly inhibited these responses too. When TL were cultured with various doses of con A in the presence of 5 or 10 micrograms Am B/ml, the shape of the dose curves resembled those of PBL stimulated in the absence of Am B except that the incorporation of 3H-thymidine increased with increasing cell density. It was concluded that Am B at 2.5-5.0 micrograms/ml enhanced the response of PBL to con A and suppressed the response at 10 micrograms/ml. All doses of Am B inhibited both spontaneous proliferation and con A-induced proliferation in TL. In spite of this inhibition, the TL population responded to various doses of con A in the presence of Am B.

Synergistic effects of lipopolysaccharide on phytohemagglutinin- and concanavalin A-induced deoxyribonucleic acid synthesis in human peripheral blood lymphocytes: participation of T lymphocytes

Lipopolysaccharide induces a synergistic uptake of tritiated thymidine in peripheral blood lymphocytes (PBL) when cultured with phytohemagglutinin or concanavalin A as compared to PBL incubated only with phytohemagglutinin or concanavalin A. In this study we investigated which subpopulations(s) of PBL is involved in this synergistic increase in deoxyribonucleic acid synthesis. Separation of PBL into sheep erythrocyte rosette-forming cells (T cells) and non-rosette-forming cells (B cells) showed that the T cells were responsible for the increased uptake of radiolabel. PBL and T cells had similar dose-response profiles and kinetic patterns. Paralleling this augmented tritiated thymidine uptake was an increase in the number of cells undergoing blast transformation. Delayed-addition experiments showed that the two mitogens must be added within 12 h of each other for maximal augmentation to occur. Finally, preincubation of T cells with lipopolysaccharide had no demonstrable effect on the amount of concanavalin A uptake by these cells. This model may provide unique information about the activation of human peripheral blood T cells compared to activation of these cells by one mitogen.

Characterization of the role of mononuclear cell subpopulations in the in vitro lymphocyte proliferation assay

Purified human mononuclear cell subpopulations have been evaluated in the in vitro lymphocyte proliferation assay. Monocyte-depleted mononuclear cells had reduced or absent responses to mitogens and antigens which could be restored to the original mononuclear cell response by addition of purified plastic adherent cells. Purified T lymphocytes obtained by density gradient centrifugation of E-rosette-forming cells demonstrated low but significant proliferative responses to mitogens, but no significant response to antigens. The addition of monocytes potentiated the response of purified T cells to mitogens and antigens, but did not fully reconstitute the original mononuclear cell response unless non-T lymphocytes were also present. It is concluded that mononuclear cell proliferation represents a complex mechanism of cellular interaction involving multiple subpopulations of cells.

Nonspecific and specific immunological mitogenicity by group A streptococcal pyrogenic exotoxins

Group A streptococcal pyrogenic exotoxin (SPE) types A, B, and C induced lymphocyte proliferation both specifically and nonspecifically, and the responses showed characteristics associated with both types of stimulation. Guinea pig lymphocytes from animals presensitized to SPE A displayed immunologically specific proliferation in response to SPE A; control lymphocytes showed little activity in the presence of SPE A. Lymphocytes from guinea pigs not presensitized to SPE responded nonspecifically to SPE types B and C. Guinea pig lymphocytes from SPE A-presensitized animals showed enhanced proliferation over controls when treated with SPE B, suggesting that a degree of cross-reactivity between SPE types may exist, though they are serologically distinct. Mouse splenic lymphocytes exhibited low-level responsiveness to all SPE types, as would be expected for an antigen-specific proliferative response. Unlike mouse splenic lymphocytes, rabbit spleen cells and human cord blood, lymphocytes responded nonspecifically to all SPE types. Although rabbit spleen cells and human cord blood lymphocytes responded nonspecifically, the maximum response occurred at day 4 or 5, comparable to an antigen-specific system rather than a day 2 or 3 such as that with the nonspecific thymus-derived cell mitogen, concanavalin A.