Effector and regulatory T cells derived from the same T cell clone differ in MHC class II-peptide multimer binding.

MHC class II-peptide multimers are a valuable tool for antigen-specific detection of CD4(+) T cells. However, it has been proposed that T cells in a hypo-responsive state can have diminished binding of such multimers. In the present study, we investigated this phenomenon at the clonal level. We found that anergic CD4(+) T cells had a reduced capacity to bind MHC class II-peptide multimers compared to their non-anergic counterparts. Increasing the incubation temperature, time, or MHC-peptide valency could not equalize multimer binding by anergic and non-anergic T cells. Neither anergic T cells nor non-anergic T cells internalized the MHC class II-peptide dimers efficiently, and in both cases the dimers bound to the plasma membrane at locations containing a low amount of raft-associated lipids. Disruption of lipid rafts, however, led to decreased dimer binding by non-anergic T cells and to a lesser extent by anergic T cells. Finally, we show that the depth of the anergic state of the T cell, which determines its ability to regulate other T cell responses, correlates with the reduced dimer binding. We here demonstrate for the first time differential MHC class II-peptide multimer binding by regulatory (anergic) and effector T cells with identical TCR.

Achievement of a synergistic adjuvant effect on arthritis induction by activation of innate immunity and forcing the immune response toward the Th1 phenotype.

OBJECTIVE: To apply and analyze the mechanisms of action of dimethyldioctadecylammonium bromide (DDA), a powerful adjuvant that does not have the side effects of the conventionally used Freund's adjuvants, in proteoglycan-induced arthritis (PGIA) and collagen-induced arthritis (CIA). METHODS: PGIA and CIA were generated using standard immunization protocols with cartilage proteoglycan aggrecan (PG) or human type II collagen (CII) emulsified with Freund's complete adjuvant (CFA), and compared with PGIA and CIA generated using immunization protocols in which the same antigens were used in combination with the adjuvant DDA. Immune responses to immunizing and self PGs and CII, and the incidence, severity, and onset of arthritis were monitored throughout the experiments. In addition, a new, inexpensive, and powerful method of inducing arthritis using crude cartilage extracts is described. RESULTS: A significantly reduced onset period and a more severe arthritis were achieved in BALB/c mice immunized with cartilage PGs in DDA. PGs from bovine, ovine, and porcine cartilage, which otherwise have no effect or have only a subarthritogenic effect, and crude extracts of human osteoarthritic cartilage induced a 100% incidence with a very high arthritis score in BALB/c mice. The overall immune responses to either CII or PG were similar in antigen/CFA-immunized and antigen/DDA-immunized animals, but the Th1/Th2 balance shifted significantly toward a Th1 bias in DDA-injected animals with either PGIA or CIA. CONCLUSION: DDA, which was first used in autoimmune models, is a potent nonirritant adjuvant, which eliminates all undesired side effects of the Freund's adjuvants. DDA exerts a strong stimulatory effect via the activation of nonspecific (innate) immunity and forces the immune regulation toward Th1 dominance. These lines of evidence also suggest the possibility that seemingly innocuous compounds may exert an adjuvant effect in humans and may create the pathophysiologic basis of autoimmunity in susceptible individuals via the activation/stimulation of innate immunity.

Contrasting contributions of complementarity-determining region 2 and hypervariable region 4 of rat BV8S2+ (Vbeta8.2) TCR to the recognition of myelin basic protein and different types of bacterial superantigens.

In experimental autoimmune encephalomyelitis (EAE) of LEW rats, BV8S2(+) (V(beta)8.2) T cells dominate the RT1B(l)-restricted response to guinea pig myelin basic protein (gpMBP), and respond to the superantigens (SAg) Staphylococcus enterotoxin C1 (SEC1), Mycoplasma arthritidis SAg (MAS) and Yersinia pseudotuberculosis mitogen (YPM). T cells expressing the closely related BV8S4 differ from BV8S2 T cells in their response to gpMBP, and the SAg SEC1 and MAS, but not in their response to YPM. The functional differences between BV8S2 and BV8S4, which vary in complementarity-determining/hypervariable region 4 (CDR4/HV4) and CDR2, were analyzed by cloning and mutating a TCR with features typical for gpMBP-specific BV8S2(+) TCR. The wild-type BV8S2 receptor and the BV8S4-like CDR2 + 4beta double mutant of BV8S2 showed the same differences in ligand specificity as polyclonal BV8S2(+) and BV8S4(+) lymphocyte populations. The CDR2beta mutant lost its reactivity for SEC1 and gpMBP(68-88), but the CDR4/HV4beta mutation abolished only activation by SEC1. Thus, CDR2 and HV4 contribute not only differently to recognition of peptide antigens, but also to recognition of different types of bacterial SAg.