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A J Infante

Publications and source records attributed to A J Infante.

At least 37 records · Page 2Linked to original sources
PubMed1994

Highly conserved TCR beta chain CDR3 sequences among immunodominant acetylcholine receptor-reactive T cells in murine myasthenia gravis.

In C57BL/6 (B6) mice, the T cell response to acetylcholine receptor from Torpedo californica (TAChR) provides a specific antibody response and symptoms of muscular weakness similar to those displayed in the human disease myasthenia gravis. We had found previously that the B6 T cell response to AChR shows limited clonality, both in terms of the epitopes recognized and in terms of the diversity of the TCR V beta gene segments used. We now report that all TAChR-reactive B6 T cell clones which responded to the dominant antigenic epitope and expressed the dominant TCR V beta 6 gene segment exhibited conservation of amino acid sequence in the VDJ junctional region (CDR3) of the TCR beta chain. The conserved sequence motif contained a glutamic acid residue in the CDR3 of TCR beta. Analysis of TCR beta sequences from antigen-primed lymph node cells (LNC) showed a similar enrichment for sequences having a glutamic acid in CDR3, although the overall appearance of the LNC sequences was somewhat more heterogeneous and consistent with a gradual in vitro selection of the subset of TCR found in the T cell clones. As the first example of TCR sequences in this model of myasthenia gravis, these results begin to provide a context for understanding self-non-self discrimination of AChR. In particular, the unusually conserved CDR3 sequence suggests that the conserved V beta gene utilization seen previously is directly related to recognition of the immunodominant peptide epitope in association with the experimental autoimmune myasthenia gravis-susceptibility determining MHC class II molecule I-Ab.

Amino Acid Sequence↗
PubMed1994

Successful treatment of neutropenia in the hyper-immunoglobulin M syndrome with granulocyte colony-stimulating factor.

PATIENT: A young boy with hyper-immunoglobulin M (IgM) syndrome had recurrent severe infections, failure to thrive, and chronic neutropenia for 2 years despite treatment with i.v. gammaglobulin (IVIG). METHODS AND RESULTS: With the addition of granulocyte colony-stimulating factor (G-CSF; Filgrastim, Amgen, Inc., Thousand Oaks, CA), increased doses of IVIG, and prophylactic trimethoprim-sulfamethoxazole, his absolute neutrophil count increased from 0.64 x 10(9)/L to 3.36 x 10(9)/L, and he has been free of significant infection for the past 22 months. CONCLUSIONS: The use of G-CSF merits consideration in patients with hyper-IgM syndrome and severe neutropenia.

Child↗
PubMed1992

Preferential use of a T cell receptor V beta gene by acetylcholine receptor reactive T cells from myasthenia gravis-susceptible mice.

Experimental autoimmune myasthenia gravis (EAMG) is an important model for testing current concepts in autoimmunity and novel immunotherapies for autoimmune diseases. The EAMG autoantigen, acethylcholine receptor (AChR), is structurally and immunologically complex, a potential obstacle to the application of therapeutic strategies aimed at oligoclonal T cell populations. Inasmuch as we had previously shown that the clonal heterogeneity of T cell epitope recognition in EAMG was unexpectedly limited, we examined TCR V beta expression. AChR primed lymph node T cells and established AChR reactive T cell clones from EAMG-susceptible C57BL/6 (B6; H-2b, Mls-1b) mice showed preferential utilization of the TCR V beta 6 segment of the TCR. After in vivo priming and in vitro restimulation for 7 days with AChR or a synthetic peptide bearing an immunodominant epitope, V beta 6 expressing lymph node cells (LNC) were expanded several-fold, accounting for up to 75% of recovered viable CD4+ cells. The LNC of B6.C-H-2bm12 (bm12; H-2bm12, Mls-1b) mice, which proliferated in response to AChR but not to the B6 immunodominant peptide, failed to expand V beta 6+ cells. Inasmuch as nonimmune bm12 and B6 animals had similar numbers of V beta 6+ LNC (4-5%), this suggested that structural requirements for TCR recognition of Ag/MHC complexes dictated V beta usage. Results concerning peptide reactivity and V beta 6 expression among T cells from (B6 x bm12)F1 animals also suggested that structure-function relationships, rather than negative selection or tolerance, accounted for the strain differences between B6 and bm12. To examine the potential effects of thymic negative selection of V beta 6+ cells on the T cell response to AChR, CB6F1 (H-2bxd, Mls-1b; V beta 6-expressing) and B6D2F1 (H-2bxd, Mls-1axb; V beta 6-deleting) strains were analyzed for AChR and peptide reactivity and V beta 6 expression. Both F1 strains responded well to AChR but the response of B6D2F1 mice to peptide was significantly reduced compared to CB6F1. Short and long term cultures of peptide-reactive B6D2F1 LNC showed no expansion of residual V beta 6+ cells, although similar cultures of CB6F1 LNC were composed of more than 60% V beta 6+ cells. The results from the F1 strains further indicated that the T cell repertoire for peptide was highly constrained and that non-V beta 6 expressing cells could only partially overcome Mls-mediated negative selection of V beta 6+ TCR capable of recognizing peptide.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Determinant selection in murine experimental autoimmune myasthenia gravis. Effect of the bm12 mutation on T cell recognition of acetylcholine receptor epitopes.

C57BL/6 (B6) mice respond to immunization with acetylcholine receptor (AChR) from Torpedo californica as measured by T cell proliferation, antibody production, and the development of muscle weakness resembling human myasthenia gravis. The congenic strain B6.C-H-2bm12 (bm12), which differs from B6 by three amino acid substitutions in the beta-chain of the MHC class II molecule I-A, develops a T cell proliferative response but does not produce antibody or develop muscle weakness. By examining the fine specificity of the B6 and bm12 T cell responses to AChR by using T cell clones and synthetic AChR peptides, we found key differences between the two strains in T cell epitope recognition. B6 T cells responded predominantly to the peptide representing alpha-subunit residues 146-162; this response was cross-reactive at the clonal level to peptide 111-126. Based on the sequence homology between these peptides and the T cell response to a set of truncated peptides, the major B6 T cell epitope was determined to be residues 148-152. The cross-reactivity of peptides 146-162 and 111-126 could also be demonstrated in vivo. Immunization of B6 mice with either peptide primed for T cell responses to both peptides. In contrast, immunization of bm12 mice with peptide 111-126 primed for an anti-peptide response, which did not cross-react with 146-162. Peptide-reactive T cells were not elicited after immunization of bm12 mice with 146-162. These results define a major T cell fine specificity in experimental autoimmune myasthenia gravis-susceptible B6 mice to be directed at alpha-subunit residues 148-152. T cells from disease-resistant bm12 mice fail to recognize this epitope but do recognize other portions of AChR. We postulate that alpha-148-152 is a disease-related epitope in murine experimental autoimmune myasthenia gravis. In this informative strain combination, MHC class II-associated determinant selection, rather than Ag responsiveness per se, may play a major role in determining disease susceptibility.

Amino Acid Sequence↗
PubMed1991

Cellular immune response of a marsupial, Monodelphis domestica.

Marsupials are interesting subjects for studies of comparative and developmental immunology because they separated from eutherian mammals over 100 million years ago and because the newborns are still in a fetal state. We studied cellular immunity in a fully pedigreed colony of the marsupial, M. domestica (commonly called the gray short-tailed opossum). Peripheral blood lymphocytes were separated on nylon wool columns into adherent cells bearing surface immunoglobulin (B cells) and nonadherent cells (T cells) recovered in the ratio of 1:3. Peripheral blood lymphocytes responded by proliferation to Con A and other mitogens. Nonadherent cells were responsive to Con A, but adherent cells were not. Peripheral blood lymphocytes were stimulated weakly or not at all by allogeneic or xenogeneic (mouse) cells in mixed lymphocyte culture. Despite the weak MLC response, which was not due to genetic homogeneity, allogeneic and xenogeneic tail skin grafts were rejected promptly. These data suggest that the cellular immune response of M. domestica is similar to that of eutherian mammals with the notable exception of weak MLC responses.

Animals↗
PubMed1990

Virus-induced interferon alpha/beta (IFN-alpha/beta) production by T cells and by Th1 and Th2 helper T cell clones: a study of the immunoregulatory actions of IFN-gamma versus IFN-alpha/beta on functions of different T cell populations.

Spleen cells, resting T cells, activated T cells, and T cell clones characterized as type 1 (Th1) and type 2 (Th2) were investigated for their ability to produce interferon (IFN) following in vitro culture with Newcastle disease virus (NDV). All of the above cell populations, including both Th1 and Th2 T cell clones, produced high levels of IFN following in vitro culture with NDV. This IFN was characterized as a mixture of IFN-alpha and IFN-beta with IFN-alpha being the predominate species of IFN contained in the mixture. IL-2 greatly enhanced the production of IFN-alpha/beta by all cell populations in response to NDV. These different T cell populations responded very differently to the immunoregulatory actions of IFN-gamma versus IFN-alpha/beta. IFN-alpha/beta was shown to be a potent inhibitor of Con A or IL-2-induced proliferation of different T cell populations. This inhibition was not associated with a reduction in lymphokine production since spleen cells or Th1 T cell clones cultured with Con A and IFN-alpha/beta had no decrease in IL-2 or IFN-gamma production when compared to Con A-stimulated control cultures. IFN-gamma had little to no inhibitory activity on Con A-induced proliferation of spleen cells. In fact, Con A-induced proliferation was usually enhanced by IFN-gamma when nylon wool-enriched T cells were assessed. Different results were observed when IFN-gamma and IFN-alpha/beta were investigated for their ability to inhibit IL-2-induced proliferation of different T helper cell clones. IFN-gamma and IFN-alpha/beta were both capable of inhibiting IL-2-induced proliferation of T cell clones characterized as type 2 (Th2). In contrast, IFN-gamma had no effect on IL-2-induced proliferation of Th1 clones. IFN-alpha/beta, however, inhibited IL-2-induced proliferative responses of both Th1 and Th2 T cell clones. These results document the facts that (1) IFN-gamma and IFN-alpha/beta differ in their immunoregulatory actions, (2) different T cell subpopulations vary in their susceptibility to IFN-gamma regulation, and (3) virus induction of IFN-alpha/beta appears to be a ubiquitous function associated with different T cell populations.

Animals↗
PubMed1989

Synergistic activation of granulocyte-macrophage colony-stimulating factor production by IL-1 and IL-2 in murine Th1 cells.

Recent reports indicate that murine CD4+ Th1-type cloned T cells are insensitive to IL-1 because specific IL-1R are not detected on these cells and IL-1 does not modulate proliferative responses. However, we have determined that Th1 clones can respond to IL-1, because they function synergistically with IL-2 to induce granulocyte-macrophage-CSF secretion. This response to IL-1 plus IL-2 could be induced by IL-1 alpha or IL-1 beta and by membrane-bound IL-1 on macrophages. However, IL-1R could not be detected, and Th1 cells did not respond to IL-4 in the presence or absence of IL-1, as measured by either proliferation or granulocyte-macrophage-CSF production. Therefore, IL-1 functioned as a cofactor in Th1 cells stimulated with IL-2, but not with IL-4. A possible mechanism whereby IL-1 activates Th1 cells is discussed.

Animals↗
PubMed1989

Restricted idiotypic profile of anti-phosphorylcholine antibodies induced by carrier-specific helper T cell clones.

The primary antibody response of C57BL/6 mice to phosphorylcholine (PC) is dominated by immunoglobulins of the T15 idiotype family. Using monoclonal antibodies that define individual idiotopes (Id) of T15, it has been shown that the antibody plaque-forming cells (PFC) arise from heterogeneous population of B cells that may express some but not all T15 Id. In the present study, we tested the ability of antigen (keyhole limpet hemocyanin, KLH)-specific CD4+ T cell clones (Th) to provide help for various T15 B cell subsets in response to PC-KLH in vitro. Four independently derived, KLH-specific Th clones were found to provide quantitative help (80-120 PFC/culture of 10(6) B cells) which was comparable to KLH-primed, unselected T cells. However, the response in the presence of the cloned T cells was idiotopically restricted: T15 idiotopes B24-44 and B36-75 were expressed on 60% to 90% PFC, whereas Id AB1-2 and B36-82 were not present (0%-20% PFC). All of these Id were highly expressed in cultures with KLH-primed, unselected splenic T cells. Evidently, the cloned Th cells provided help to only a subset of idiotypically distinct B cells. Bulk spleen T cells from unprimed donors by themselves did not provide any help for the primary response to PC-KLH. However, when these cells were added to the cultures containing B cells and KLH-specific Th clones, the repertoire of the response was fully restored, including the AB1-2/B36-82 Id (50%-80% PFC). These results suggest the existence of an auxiliary helper mechanism that may be required for activation of some B cells in addition to the antigen-specific Th cells.

Animals↗
PubMed1989

Collaboration of Th1 and Th2 T cell clones in specific antibody responses: regulation of the IgM response to phosphorylcholine.

Carrier (KLH)-specific type 1 T cell clones (Th1), which are defined by secretion of IL-2 and IFN-gamma but not IL-4, and type 2 (Th2) clones, which secrete IL-4, but not IL-2 or IFN-gamma, have been isolated and analyzed for their ability to collaborate in providing help for B cells to secrete phosphorylcholine-specific IgM antibodies. The resulting antibody responses exhibited a characteristic pattern suggesting two distinct regulatory interactions among the Th1, Th2, and B cells. At low doses of antigen, Th1 cells enhanced the helper function of the Th2 cells, an effect due primarily to IL-2. At high doses of antigen, Th1 cells or IFN-gamma inhibited Th2-dependent antibody responses. The inhibitory effect of Th1 or IFN-gamma affected primarily the hapten-carrier-linked portion of the response. The overall effect was a modulation of the antigen dose-response curve for antibody production, eliminating the sharp increases in dose response mediated by isolated T cell clones. The data suggest that collaborative interactions of Th1 and Th2 cells in antibody production may have important physiological consequences.

Animals↗
PubMed1988

L3T4+ T cells regulate Abelson virus-induced lymphomagenesis.

To evaluate the role of T cells in regulation of lymphomagenesis, experiments were performed using Abelson murine leukemia virus (AMuLV). In vitro transformation of bone marrow target cells by this B lymphotropic retrovirus was inhibited by peripheral lymph node cells from naive mice. The inhibitory activity depended on Thy-1+ L3T4+ cells but did not require Lyt-2+ cells. In vivo depletion of L3T4+ T cells with a mAb (GK1.5) altered the course of AMuLV-induced lymphoma. L3T4 depletion of naturally resistant C57BL/6 mice resulted in dramatic susceptibility to lymphoma induction. Lymphoma cells from anti-L3T4-treated C57BL/6 mice infected with AMuLV displayed the B lineage transformation marker P1606C3. These studies reveal an important immunologic component of Abelson disease resistance involving L3T4+ T cells.

Abelson murine leukemia virus↗
PubMed1988

Identification and characterization of a mouse cell surface antigen with alternative molecular forms.

We present the characterization of a new mouse cell surface protein, recognized by the 3E8-specific monoclonal antibody. The expression of this antigen is predominantly restricted to the hematopoietic and lymphoid tissues: bone marrow, spleen, lymph node, and thymus. Immunoblot analyses show that the 3E8 determinant is present on molecules with different apparent relative masses. The 3E8 antigen migrates on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a single band of Mr 115,000 for normal nonstimulated spleen cells and thymocytes and as two bands of Mr 115,000 and Mr 125,000 for bone marrow cells and mitogen-stimulated spleen cells. The multiple sizes of the 3E8 antigens (isoforms) found on various cell lines are not due to allelic polymorphism, but instead may reflect the specific cell type or reflect the cell's state of activation or maturation. Results from lectin chromatography and N-glycanase and neuraminidase studies suggest that the 3E8 antigen is a heavily sialylated O-linked glycoprotein. The unusual features of this antigen indicate that it may be the mouse homologue of the rat W3/13 antigen and the human leukosialin/sialophorin antigens.

Animals↗
PubMed1986

Transferrin synthesis by inducer T lymphocytes.

Transferrin (Tf) is a growth factor that transports iron in plasma. It is essential for proliferation of activated T lymphocytes. Previous studies have suggested that peripheral blood cells are capable of synthesizing Tf. Using in situ hybridization techniques and human Tf complementary DNAs as probes, peripheral blood cells have been examined for sites of Tf messenger RNA (mRNA) transcription. The studies described here demonstrate that Tf is synthesized by a specific subset of T lymphocytes, the T4+ inducer subset. T lymphocyte proliferation is dependent upon the presence of both interleukin 2 (IL-2) and Tf, even though resting cells do not possess receptors for either. The present studies indicate that during T cell activation, induction of IL-2 mRNA transcription and IL-2 receptor expression precede the transcription of Tf mRNA and expression of Tf receptors, respectively. These events in turn precede the initiation of DNA synthesis. Transferrin and its receptor appear to be involved in an autocrine pathway which is functionally linked to the IL-2/IL-2 receptor autocrine loop.

Cell Cycle↗
PubMed1984

Multiple functional sites on a single Ia molecule defined using T cell clones and antibodies with chain-determined specificity.

Monoclonal antibodies (mAb) were used to inhibit the proliferation of antigen-reactive (C57BL6/J X A/J)F1 restricted T cell clones. We have been able to subdivide these F1 restricted T cell clones into two groups: one of which recognizes the A alpha k A beta b molecule and the other group which recognizes the A alpha b A beta k molecule. Using clones with defined reactivities, we could assign the reactivities of monoclonals to the A alpha or A beta chains. By immunoprecipitation and two-dimensional analysis of Ia molecules from F1 spleen cells, we could independently map the reactivities of the mAb as being determined by the A alpha or A beta chain. To date, these two methods of chain localization of the antibody reactivity have agreed. Further, the differential blocking of the A alpha k A beta b restricted T cell clones suggests that there exists more than one restriction site per Ia molecule. Increasing the number of possible functional Ia restriction sites, either through combinatorial association of alpha and beta chains or by using more than one site per molecule, should increase the number of ways Ia molecules can function in antigen presentation.

Animals↗
PubMed1983

Biochemical characterization of B lymphoma cell antigen processing and presentation to antigen-reactive T cells.

Generating an immune response to T-dependent antigens requires the cooperative interaction of APC, T helper cells, and B cells. T helper cells recognize antigen, not as soluble, native antigen, but as processed antigen in association with Ia molecules on the surface of an APC. Investigators from our laboratory demonstrated previously that some B lymphoma cell lines will present antigen to antigen-reactive T cells in an MHC-restricted fashion. These tumor lines are used in this study as a model system to examine the biochemical basis of antigen processing. Five different H-2d tumor cell lines, which differ in their ability to express Ia molecules and function as APC, are all shown to biochemically degrade sperm whale Mb in a similar manner. Intact Mb and four Mb fragments (4.3 to 12.5 Kd) were reproducibly recovered from each of these Mb-pulsed cell lines. This processed Mb is shown to be nonrandomly distributed in external and internal compartments, with the two smallest Mb fragments being enriched in the intracellular compartment. The Mb and Mb fragments can be completely removed from the surface of the APC by enzymatic proteolysis without quantitatively changing the ability of these cells to present Mb to Mb-reactive T cell lines. These results suggest that the processed Mb that is located intracellularly is the primary immunoreactive antigen for antigen presentation to T helper cells.

Animals↗
PubMed1982

T cell clones specific for hybrid I-A molecules. Discrimination with monoclonal anti-I-Ak antibodies.

Alloreactive and soluble antigen-reactive, I-A-restricted T cell clones were examined for their ability to recognize hybrid I-A antigens. Several clones that recognized hybrid I-A(b)/I-A(k) molecules on (C57BL/6 x A/J)F(1) [(B6A)F(1)] spleen cells were studied. We were able to distinguish clones that recognized hybrid I-A molecules of the A(b)(a)A(k)(beta) type from those that recognized A(k)(a)A(b)(beta) molecules. We reached this conclusion by considering data from three independent types of experiments. (a) Monoclonal antibodies were used to inhibit T cell stimulation. Antibodies 10.2.16 and H116.32 distinguished two mutually exclusive "families" of T cell clones. One group of clones was inhibited by 10-2.16 and not H116.32, the other group exhibited reciprocal inhibition. (b) T cell proliferation was assayed using antigen-presenting cells from B6.C-H-2(bml2) (bml2) and [bml2 x B10.A(4R)]F(1) mice. Because the bml2 strain has a mutation that results in an altered A(b)(beta) polypeptide chain (A(bm12)(beta)), we reasoned that clones that could recognize the [bm12 x B 10.A(4R)]F(1) cells were recognizing A(b)(a)A(k)(beta) molecules. Alternatively, clones not recognizing [bml2 x B10.A(4R)]F(1) cells had specificity for A(k)(a)A(b)(beta) molecules. (c) I-A molecules immunoprecipitated from radiolabeled (B6A)F(1) splenocyte extracts were analyzed by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These experiments confirmed an earlier report that antibody 10.2.16 recognized determinants on the A(k)(beta) chain (12). Antibody H116.32 immunoprecipitated products consistent with recognition of A(k)(a) determinants. Taken together, these three types of results offer conclusive evidence that T cell clones recognizing "hybrid" I-A molecules use either A(b(k)A(k)(beta) or A(k)(a)A(b)(beta) molecules as recognition or restriction sites. Clones whose proliferation was supported by [bm 12 x B10.A(4R)]F(1) cells and blocked by anti-I-A(k) antibody 10-2.16 recognized A(b)(a)A(k)(beta) B molecules. Clones that were blocked by antibody H116.32 and did not recognize [bml2 X B10.A(4R)]F(1) cells use a recognition site(s) on A(b)(a)A(k)(beta) molecules. Thus, we can demonstrate both functionally and biochemically that hybrid F(1) I-A molecules of the structure A(k)(a)A(b)(beta) and A(b)(a)A(k)(beta) both exist on (B6A)F(1) splenocytes and that both configurations are used in immune recognition phenomena.

Animals↗
PubMed1982

Definition of T cell idiotypes using anti-idiotypic antisera produced by immunization with T cell clones.

Alloreactive T cell clones with distinct specificities were used to raise anti-idiotypic antisera via an F1 anti-(parent anti-F1) protocol. Antisera were raised that could stimulate the proliferation of the appropriate T cell clone, but not other clones. The active fraction of the antisera for T cell proliferation was immunoglobulin. In addition to proliferation, an anti-idiotypic antiserum could induce the appropriate T cell clone to secrete substantial amounts of interleukin 2 (IL-2). Production of IL-2 appeared independent of the involvement of accessory cells. These accessory cells may be unnecessary for IL-2 production in our assay, or their effect may be produced by anti-idiotype. Thus, anti-idiotype may provide two or more specific T cell signals.

Animals↗