Ia-antigen-T-cell interactions for a thymus-independent antigen composed of D amino acids.

Abstract

Synthetic polypeptide antigens of L amino acids, although bearing repeating sequences, are thymusdependent (L-TD), whereas the same polymers composed of D amino acids are thymus-independent (D-TI), probably due to a slower rate of metabolism. Yet we found that lymph-node cells of BALB/c mice immunized with D-TI proliferate in response to it in vitro. To follow T-cell activation by D-TI, we established T-cell hybridomas to D-TI and to its analog composed of L isomers, L-TD, for comparison. The T-cell hybridomas express membrane a/fl T-cell receptors and secrete interleukin 2 upon stimulation with the respective antigen. In addition, D-TIspecific hybridomas are stimulated, to a lesser extent, by the L-TD antigen, whereas only some L-TD-specific hybridomas recognize D-TI. Moreover, biotinylated analogs of D-TI and L-TD bind to splenic antigen-presenting cells (APCs) from BALB/c mice. Binding is inhibited by an excess of nonbiotinylated L-TD, and by an excess of a peptide comprising residues 259-271 of the human acetylcholine receptor a subunit, which binds to I-Ad and I-Ed molecules without prior processing. Analysis of APC lysates following incubation of the APCs with biotinylated D-TI and L-TD reveals that the biotinylated antigen moiety is associated with Ia molecules. D-TI and L-TD bind to Ia molecules on intact APCs with similar KD values, 5 x 10-8 M and 3 x 10-8 M, respectively. However, D-TI has faster kinetics of binding than L-TD, probably due to different processing requirements. Hence, we have demonstrated a major histocompatibility complex class Il-mediated T-cell response to a thymus-independent antigen. poly(DLAla)--poly(Lys) [a poly(Lys) backbone with Tyr-TyrGlu-Glu-poly(DLAla) side chains] (9).Another important feature of TI antigens is a slow rate of metabolism (10, 11), which results in persistence of detectable amounts of antigens in macrophages of the spleen and lymph nodes several weeks after immunization (10,12). Thus, (Tyr-Glu-Tyr-Glu)-poly(DLAla)--poly(Lys), which is slowly metabolized by macrophages, is TI, whereas the analog with the faster clearance, (Tyr-Tyr-Glu-Glu)-poly(DLAla)--poly(Lys), is TD (13). Similarly, a branched polypeptide that is built of L amino acids, poly(Phe,Glu)-poly(Pro)--poly(Lys), is TD (L-TD), whereas its analog that is composed of D isomers of the same amino acids, poly-(DPhe,DGlu)-poly(DPro)--poly(DLys), is TI (D-TI), probably due to its slow degradation.Subsequently it was shown that extensive depletion of T cells from splenic lymphocyte populations significantly reduced the in vitro B-cell responses to TI antigens. The latter responses required, in addition to T cells, Ia-bearing adherent cells (14).In this paper we describe the establishment and characterization of T-cell hybridomas specific to the TI branched polypeptide D-TI, in comparison to T-cell hybridomas specific to L-TD, a polypeptide that has the same amino acid composition but of L isomers. In addition, we show that D-TI is presented to T cells by Ia molecules on antigen-presenting cells (AP...

Activating an adaptive immune response from a hydrogel scaffold imparts regenerative wound healing

“…The adaptive immune system recognizes non-self-peptide antigens to induce cell mediated (T cell) and humoral (B cell) immunity. Peptides containing D-amino acids have been reported to activate or suppress T cell dependent and T cell independent adaptive immune responses 5 , 32 . In the context of the MAP, cross-linking peptides that are non-native may be presented to the immune system until fully degraded.…”

Direct binding of myelin basic protein and synthetic copolymer 1 to class II major histocompatibility complex molecules on living antigen-presenting cells--specificity and promiscuity.

“…Whereas both methods do not require the isolation of the individual MHC alleles, the use of biotinylated peptides to monitor their binding to the MHC is advantageous, since it measures only peptides bound to the surface MHC molecules on intact cells (14,16,19). This approach can be utilized (20,21) to demonstrate the binding not only of short peptides but also of larger molecules. Thus, by using biotinylated poly(L-Tyr,L-Glu)-poly(DL-Ala)--poly(L-Lys), a synthetic multichain polypeptide antigen of L-amino acids, and poly(D-Phe,D-Glu)-poly(D-Pro)--poly(DLys), a synthetic polymer composed of D-amino acids, this method was exploited to measure equilibrium and kinetics of binding to the MHC and the processing requirements (20,21 (Bicester, England).…”

“…This approach can be utilized (20,21) to demonstrate the binding not only of short peptides but also of larger molecules. Thus, by using biotinylated poly(L-Tyr,L-Glu)-poly(DL-Ala)--poly(L-Lys), a synthetic multichain polypeptide antigen of L-amino acids, and poly(D-Phe,D-Glu)-poly(D-Pro)--poly(DLys), a synthetic polymer composed of D-amino acids, this method was exploited to measure equilibrium and kinetics of binding to the MHC and the processing requirements (20,21 (Bicester, England). SJL/J and (BALB/c x SJL/J)F1 mice were obtained from The Jackson Laboratory.…”

T-Cell-Independent Responses toBorrelia burgdorferiAre Critical for Protective Immunity and Resolution of Lyme Disease

“…These findings, and parallel results obtained with B. burgdorferi-infected mice treated with a monoclonal antibody that inhibits the B7-CD28 costimulatory pathway (31), also suggest either that T cells are not necessary for protective and arthritis-resolving antibody responses to B. burgdorferi or that T cells may regulate the immune response to some TI antigens via nonclassical pathways. Apparently, under some circumstances TI antigens have been shown to directly stimulate T cells (13,33,40,42).…”