CD8 T-cell responses against the immunodominant Theileria parva peptide Tp249-59 are composed of two distinct populations specific for overlapping 11-mer and 10-mer epitopes

Immunity against Theileria parva is associated with CD8 T‐cell responses that exhibit immunodominance, focusing the response against limited numbers of epitopes. As candidates for inclusion in vaccines, characterization of responses against immunodominant epitopes is a key component in novel vaccine development. We have previously demonstrated that the Tp2_49–59 and Tp1_214–224 epitopes dominate CD8 T‐cell responses in BoLA‐A10 and BoLA‐18 MHC I homozygous animals, respectively. In this study, peptide–MHC I tetramers for these epitopes, and a subdominant BoLA‐A10‐restricted epitope (Tp2_98–106), were generated to facilitate accurate and rapid enumeration of epitope‐specific CD8 T cells. During validation of these tetramers a substantial proportion of Tp2_49–59‐reactive T cells failed to bind the tetramer, suggesting that this population was heterogeneous with respect to the recognized epitope. We demonstrate that Tp2_50–59 represents a distinct epitope and that tetramers produced with Tp_50–59 and Tp_49–59 show no cross‐reactivity. The Tp2_49–59 and Tp2_50–59 epitopes use different serine residues as the N‐terminal anchor for binding to the presenting MHC I molecule. Molecular dynamic modelling predicts that the two peptide–MHC I complexes adopt structurally different conformations and Tcell receptor β sequence analysis showed that Tp2_49–59 and Tp2_50–59 are recognized by non‐overlapping T‐cell receptor repertoires. Together these data demonstrate that although differing by only a single residue, Tp2_49–59 and Tp2_50–59 epitopes form distinct ligands for T‐cell receptor recognition. Tetramer analysis of T. parva‐specific CD8 T‐cell lines confirmed the immunodominance of Tp1_214–224 in BoLA‐A18 animals and showed in BoLA‐A10 animals that the Tp2_49–59 epitope response was generally more dominant than the Tp2_50–59 response and confirmed that the Tp2_98–106 response was subdominant.

Transcription of the unique ruminant class II major histocompatibility complex-DYA and DIB genes in dendritic cells

Dendritic cells (DC) constitute the most effective immune cell population for priming and recalling T cell responses to foreign antigens. DC patrol the peripheral tissues collecting foreign antigen for subsequent presentation by classical class II MHC molecules to T cells in the draining lymph nodes. Since the description of the DYA and DIB class II MHC genes, which are unique to ruminants, no transcript or protein have been reported. Here we provide evidence that these genes are transcribed in cattle and that paired transcription is restricted in afferent lymph to a functionally distinct population of DC. Analysis of lymph node, lung and thymus suggests that tissue DC also transcribe both genes. Cytokine-induced differentiation of cultured monocytes to a DC phenotype is linked with induction of both DYA and DIB transcription. This is consistent with an association of their products with the potent antigen presenting capacity of these cells in cattle.

Expression of beta 2 integrins on blood leukocytes of cows with or without bovine leukocyte adhesion deficiency

Peripheral blood leukocytes of 11 normal cows, 7 cows heterozygous and 2 heifers homozygous for bovine leukocyte adhesion deficiency (BLAD) were analysed by flow cytometry for the intensity of their beta 2 integrin expression (LFA-1(CD11a/CD18), CR3 (CD11b/CD18) and CR4 (CD11c/CD18)). BLAD-homozygotes revealed no or a very weak expression of the beta 2 integrins and had a 10-fold and 4- to 5-fold increase in absolute number of neutrophils and monocytes, respectively, whereas the absolute number of lymphocytes remained normal. The mean fluorescence intensity (MFI) of the beta 2 integrins (CD18) in heterozygous animals was 56 to 90% of this in the normal cows (MFI between 14 and 512). The difference in the expression level was most pronounced for LFA-1 on the small cluster of lymphocytes with the highest MFI for LFA-1. Repeated analysis and phorbol myristate acetate stimulation revealed that the LFA-1 expression on this high-expressing cell population of the peripheral blood allowed a ready identification of BLAD-heterozygotes by flow cytometry.

An assay for the identification of antigens recognized by cytotoxic T cells, based on transient transfection of COS cells

The studies reported here describe methodology permitting the direct identification of antigens recognized by cytotoxic T lymphocytes. We demonstrated that bovine alloreactive CTL can detect a bovine MHC molecule transiently expressed in a COS cell population in a standard microcytotoxicity assay. We then showed that alloreactive CTL can detect cells expressing the bovine class I MHC molecule in a population of cells transfected with the plasmid containing the corresponding gene plus 100-fold as many plasmids containing an irrelevant gene. In addition, the transiently transfected COS cells can specifically restimulate CTL as detected by a standard microcytotoxicity assay using the target cell line. Overall, the results suggest that COS cells could be employed for the direct screening of an antigen or antigen gene library by immune CTL.

Selection of BoCD25 monoclonal antibodies by screening mouse L cells transfected with the bovine p55-interleukin-2 (IL-2) receptor gene

The bovine interleukin-2 receptor-alpha (IL-2R alpha) gene has been isolated and a rabbit antiserum against a fusion protein of the gene has been produced. However, the antiserum does not inhibit IL-2-dependent proliferation. Since a panel of monoclonal antibodies (mAb) to bovine activation antigens was available, we transfected the gene into mouse L fibroblasts, selected stable transfectants with the rabbit antiserum, and screened for antibodies that bound the transfected cells but not the untransfected cells. Three mAb were selected and all three precipitated a molecule of M(r) 55,000 (under reducing conditions) from activated cells, as expected from homology with mouse and human IL-2R alpha (CD25, Tac). One of the three mAb was a strong inhibitor of IL-2-dependent proliferation of bovine lymphocytes. Thus, the availability of transfected cells allowed us to establish quickly and unequivocally the antigenic specificity of a number of antibodies.

Cyclosporin A and steroid therapy in sixty-six cadaver kidney recipients

From nine to 18 months ago, 66 patients were given 67 randomly matched cadaveric kidneys with cyclosporin A and steroid therapy. Nine of the recipients were undergoing retransplantation. The over-all kidney survival rate to date has been 77.6 per cent, and 78.8 per cent of the recipients are dialysis-free. The patient mortality in this learning phase was 13.3 per cent. Nephrotoxicity, hepatotoxicity and other side-effects of cyclosporin A could usually be dealt with by dosage adjustments, making feasible the chronic use of this agent. One B-cell immunoblastic sarcoma was encountered which was monoclonal. It was not responsible for death. Another patient had a perforation of the intestine from a lympho-proliferative reaction in which the B cells were polyclonal. After jejunal resection a year ago, there were no further complications. This lesion was not classified as a lymphoma. Both lympho-proliferative lesions were associated with a rise in antibody to viral capsid antigen of Epstein-Barr virus. Results of this study have verified the effectiveness and relative safety of cyclosporin A with steroids for immunosuppression in human recipients of cadaveric kidneys.

Localization of Tamm-Horsfall glycoprotein in the human kidney using immuno-fluorescence and immuno-electron microscopical techniques

Small pieces of tissue obtained from apparently normal areas of four surgically removed adult human kidneys were used in the present study. The results obtained by immuno-fluorescence and immuno-electron microscopical techniques show that Tamm-Horsfall glycoprotein (THP) is present in the thick ascending limbs of the loops of Henle and the distal convoluted tubules. Within the cells concerned, the protein is associated with the luminal, lateral as well as basal, plasma membranes and their infoldings. The cells of the macula densa are completely negative as are those of proximal convoluted tubules, glomeruli and collecting ducts. The possible significance of these findings in relation to the process of urine dilution in the nephron is discussed.