Genetic Control of the T-Lymphocyte Proliferative Response to Cytochrome c

The immune response (Ir) to the random copolymer GLphi depends upon the function of two Ir genes, Ir-GLphi-beta[beta] and Ir-GLphi-alpha[alpha], mapped to the I-A and I-E/C subregions of the major histocompatibility complex, respectively. In this paper, the site(s) of expression of the products of these two Ir genes was examined by evaluating T-lymphocyte proliferative responses of bone marrow radiation chimeras. Chimeras were created in [alpha+beta- X alpha-beta+]F1 responder mice by lethal irradiation and reconstitution with a mixture of bone marrow cells from both parental strains. These chimeras failed to respond to GLphi, although they were capable or responding to the much weaker antigens, (T,G)-A--L, TEPC-15, pigeon cytochrome c, and (H,G)-A--L. This failure to respond to GLphi was shown not to be the result of a cryptic mixed lymphocyte reaction, as similar chimeras created in (alpha+beta+ X alpha-beta+)F1 mice responded well to GLphi, although they possessed almost the same potential histoincompatibility. Furthermore, the lack of response to GLphi could not be attributed to a general failure of the two parental cell types in the chimeras to collaboratc with each other, as each chimeric parental cell type could respond to dinitrophenyl conjugated ovalbumin presented on nonimmune spleen cells from the other parent. Thus, the failure of low responder parental into F1 high responder chimeras to generate an immune response to GLphi suggests that immune competence for this antigen requires at least one cell type in the immune system to express gene products of both the Ir-glphi-alpha and -beta genes, i.e. one cell must be of high responder genotype. The the antigen-presenting cell is one such cell type was shown by experiments in which GLphi-primed T lymphocytes from responder F1 mice were stimulated with antigen bound to nonimmune spleen cells. Only spleen cells from responder F1 and recombinant mice could present GLphi. Neither of the two complementing nonresponder parental spleen cell populations, either alone or mixed together, could present GLphi, although both could present purified protein derivative of tuberculin. This was shown to be the case for T cells positively selected in vitro as well as freshly explanted T cells. Thus, both Ir-GLphi-alpha and Ir-GLphi-beta gene products must be expressed in the same antigen-presenting cell to generate a T-lymphocyte proliferative response to GLphi. The implications of these findings for models of two gene complementation are discussed.

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Gene complementation in the T-lymphocyte proliferative response to poly (Glu55Lys36Phe9)n. A demonstration that both immune response gene products must be expressed in the same antigen-presenting cell.

Schwartz¹,

Yano²,

Stimpfling³

et al. 1979

“…In H-2 k or H-2 a mice, the IE k MHC class II molecule (MHCII) presents pPCC and pMCC to T cells. The phenomenology associated with the response to these peptides led to the discovery of two complementing "immune response" genes that later turned out to be the structural genes for the ␣ and ␤ chains of the IE k molecule (2). Mutational studies have predicted which of the pPCC and pMCC amino acid side chains are important for the binding of the peptides to the IE k molecule (3,4).…”

Section: Introductionmentioning

confidence: 99%

Structural Basis of Cytochrome c Presentation by IEk

Fremont

Dai

Chiang

et al. 2002

The COOH-terminal peptides of pigeon and moth cytochrome c, bound to mouse IEk, are two of the most thoroughly studied T cell antigens. We have solved the crystal structures of the moth peptide and a weak agonist–antagonist variant of the pigeon peptide bound to IEk. The moth peptide and all other peptides whose structures have been solved bound to IEk, have a lysine filling the p9 pocket of IEk. However, the pigeon peptide has an alanine at p9 shifting the lysine to p10. Rather than kinking to place the lysine in the anchor pocket, the pigeon peptide takes the extended course through the binding groove, which is characteristic of all other peptides bound to major histocompatibility complex (MHC) class II. Thus, unlike MHC class I, in which peptides often kink to place optimally anchoring side chains, MHC class II imposes an extended peptide conformation even at the cost of a highly conserved anchor residue. The substitution of Ser for Thr at p8 in the variant pigeon peptide induces no detectable surface change other than the loss of the side chain methyl group, despite the dramatic change in recognition by T cells. Finally, these structures can be used to interpret the many published mutational studies of these ligands and the T cell receptors that recognize them.

“…To demonstrate that the cyanogen bromide treatment by itself did not affect the stimulating ability of intact cytochromes c in the assay, uncleaved pigeon and duck cytochromes c were recovered from the cyanogen bromide reaction mixtures and compared to the original native preparations for their ability to stimulate a proliferative response. No differences were observed (7). PETLES from B10.A mice immunized with intact pigeon cytochrome c were challenged in vitro with equimolar concentrations of the whole molecule or the various fragments.…”

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confidence: 99%

T-lymphocyte response to cytochrome c. I. Demonstration of a T-cell heteroclitic proliferative response and identification of a topographic antigenic determinant on pigeon cytochrome c whose immune recognition requires two complementing major histocompatibility complex-linked immune response genes.

Solinger¹,

Ultee²,

Margoliash³

et al. 1979

164

The T-lymphocyte proliferative response to pigeon cytochrome c was studied in the mouse. H-2a and H-2k strains were responders to this antigen whereas H-2b, H-2d, H-2f, H-2ja, H-2p, H-2q, H-2r, H-2s, and H-2u strains were low or nonresponders. Genetic mapping demonstrated that two major histocompatibility complex (MHC)-linked Ir genes control the response, one in I-A, the other in I-E/I-C. The major antigenic determinant recognized in this response was localized by cross-stimulations with species variants and cyanogen bromide cleavage fragments of cytochrome c. It was found to be a topographic surface determinant composed of an isoleucine for valine substitution at residue 3, a glutamine for lysine substitution at residue 100 and a lysine for glutamic acid substitution at residue 104. Tobacco hornworm moth cytochrome c, which contains a glutamine at residue 100 but a terminal lysine at residue 103 (one amino acid closer to the glutamine), stimulated pigeon cytochrome c immune T cells better than the immunogen. This result demonstrates for the first time a functional T-cell heteroclitic proliferative response in a system under Ir gene control. Immunization with the cyanogen bromide cleavage fragments revealed that only pigeon cytochrome c fragment 81-104 was immunogenic. This fragment primed for a T-cell proliferative response whose specificity was nearly identical to that of the T-cell response primed for by the whole molecule, suggesting that the glutamine at 100 and the lysine at 104 form the immunodominant portion of the antigenic site. Furthermore, mixing experiments using the two cross-reacting antigens, hippopotamus cytochrome c and Pekin duck or chicken cytochrome c fragment (81-104), each of which contains only one of the two immunodominant substitutions, demonstrated that the T lymphocytes responding to the major antigenic determinant comprise a single family of clones that recognize both amino acids as part of the same determinant. Thus, two complementing MHC-linked Ir genes can control the immune response to a single antigenic determinant.