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C G Fathman

Publications and source records attributed to C G Fathman.

At least 127 records · Page 7Linked to original sources
PubMed1987

Administration in vivo of recombinant interleukin 2 protects mice against septic death.

Administration in vivo of recombinant interleukin 2 (rIL-2) to mice induces a polyclonal IgM response. When co-administered with a specific antigen, rIL-2 can enhance concentrations of murine IgM antibodies specific for the antigen by fivefold within 7 d of initial treatment. IgM antibodies that are induced after injection of rIL-2 include antibodies specific for J5, a cell wall core lipopolysaccharide (LPS) antigen that is shared by the different members of the Enterobactericeae family. We report here that mice pretreated with rIL-2 or immunized with J5 antigen 7 d before bacterial challenge were protected from septic death that is caused by intraperitoneal challenges with Escherichia coli. Optimal protection was provided by a combined J5 antigen and rIL-2 treatment. Acquisition of the rIL-2 and J5 antigen-induced protection against lethal bacterial infection coincided temporally with maximal serum IgM titers that also contained IgM antibodies specific for the J5 antigen. In passive immunization experiments, the affinity-purified IgM fraction in sera of rIL-2-treated animals was identified as necessary and sufficient for protection. The IgM-depleted serum had no protective effect. The nonspecific augmentation of host-defense mechanisms without the induction of endotoxin manifestations makes rIL-2 a potential candidate to any alternative LPS-containing vaccines for the prevention of bacterial infections by gram-negative organisms since the core LPS antigen is shared among gram-negative bacteria.

Animals↗
PubMed1986

Long-term humoral unresponsiveness in vivo, induced by treatment with monoclonal antibody against L3T4.

mAbs directed against the L3T4 molecule administered in vivo caused a severe and long lasting helper cell depletion in mice. Regeneration of the L3T4+ subpopulation occurred gradually (2-3 mo) after a single antibody treatment. Experiments were designed to examine the humoral immunocompetence of such anti-L3T4-treated animals during and after regeneration of the L3T4+ T cell subset. The animals were injected with anti-L3T4, immunized with soluble antigen, and challenged with antigen every 2 wk. Antibody responses to two antigens, sperm whale myoglobin (SpWMb) and KLH, which differ with regard to their immunogenicity, were compared. The lack of humoral immune responsiveness to either of these two antigens shorty after anti-L3T4 treatment responsiveness to either of these two antigens shortly after anti-L3T4 treatment was probably due to clonal depletion. The anti-L3T4-induced immunosuppressive effect on antibody production seemed to be determined in part by the preexisting T cell repertoire, as was suggested by the recovery of responsiveness to the highly immunogenic antigen KLH and the transient inhibitory effect of anti-L3T4 treatment in primed animals. The regenerating L3T4+ T cell subpopulation was relatively incompetent in initiating B cell responses. More than 40% of the L3T4+ T cell compartment had to recover to provide help for the production of anti-KLH antibodies, whereas elimination of 90% of the L3T4+ helper cells did not inhibit a primary anti-KLH response. Evidence for a heterogeneous composition of the L3T4+ subset came from experiments using rIL-2 in vivo. The addition of rIL-2 during early helper cell depletion improved the recovery of the humoral responsiveness without apparently affecting the kinetics of the regeneration of L3T4+ T cells. Interestingly, humoral unresponsiveness to the weakly immunogenic antigen SpWMb persisted for at least 120 d. This long lasting unresponsiveness could not be explained by clonal depletion, and suggested as one possibility that the presence of antigen during regeneration of the L3T4+ helper cell population may have influenced the ultimate T cell repertoire.

Animals↗
PubMed1986

Administration of recombinant interleukin 2 in vivo induces a polyclonal IgM response.

We studied the potential immunoenhancing effects of high doses of rIL-2 on murine T and B cell functions in vivo. Injection of rIL-2 caused a threefold or more increase in the frequencies of antigen-specific proliferative T cells, suggesting that rIL-2 initiated a polyclonal T cell response. In primary and secondary humoral immune responses, administration of rIL-2 in vivo selectively enhanced the production of IgM antibodies, whereas the IgG response was unaffected. Coadministration of rIL-2 with antigen failed to induce an isotype switch from IgM to IgG in genetically low-responding mice. Interestingly, in mice treated with rIL-2 alone (in the absence of exogenous antigen), polyclonal IgM production was induced. Polyclonal IgM production of lesser magnitude was found when mice were immunized with specific antigen in the absence of exogenous rIL-2, suggesting that local IL-2 concentrations in a primary immune response might be sufficient to elicit a polyclonal IgM response.

Animals↗
PubMed1986

Intrathymic presentation of circulating non-MHC antigens by medullary dendritic cells. An antigen-dependent microenvironment for T cell differentiation.

We present evidence for intrathymic presentation of soluble circulating antigens in vivo. Our results show that proteins of different molecular weight enter the mouse thymus rapidly after i.v. injection. The intrathymic presence of antigen was assayed by proliferation of cloned antigen-specific T helper cells, which were cocultured with purified thymic stromal cells; stromal cells were isolated and purified as lymphostromal cell complexes, which preexist in vivo. Antigen presentation copurified with non-adherent medullary dendritic cells (DC) (interdigitating cells). I-A- cortical macrophages forming thymocyte rosettes in vivo and I-A+ cortical epithelial cells forming thymic nurse cells (TNC) in vivo did not act as antigen presenting cells (APC) after antigen pulsing in vivo or in vitro. Thymic APC turn over physiologically and are rapidly replaced (within 2-5 wk) after lethal irradiation by donor bone marrow-derived cells. The frequency of thymocyte-DC interactions in vivo strictly correlates with thymic T cell differentiation, and is independent of the immune status of the animal. Fetal thymic APC seem to be secluded from antigen in the maternal circulation. Thymic DC-ROS probably represent the microenvironment where maturing T cells first encounter non-MHC antigens in the context of self-MHC antigens.

Animals↗
PubMed1986

Human T-cell clones used to define functional epitopes on HLA class II molecules.

Polyclonal reagents have been used to define HLA class II molecules in conventional serologic and cellular typing. We generated human alloreactive T-cell clones to analyze the functional fine specificities of HLA class II molecules that might be important for the phenomenon of HLA and disease association. We chose to examine HLA-Dw14, an HLA-D specificity that has been associated with juvenile rheumatoid arthritis. In this paper we have presented data that suggest that conventional cellular typing does not reflect the distribution of T-cell epitopes on major histocompatibility complex class II molecules. We describe three alloreactive T-cell clones that have defined three separate Dw14-associated T-cell epitopes. Two of these epitopes were on a DR-region molecule; the third was located on a DQ-region product. In a panel of unrelated DR4-positive donors, these three DW14-associated determinants were present in a high frequency but were not linked to each other. Within the tested panel of DR4-positive cells, all possible combinatorial arrangements of these three allodeterminants were seen. The concurrent expression of any two of the three allodeterminants was equivalent to a positive typing response for Dw14. Our finding that HLA-Dw14 is not characterized by a unique allodeterminant but by the combinatorial recognition of independently distributed T-cell interaction sites suggests that analysis of HLA and disease association may be more clearly demonstrated through the use of human T-cell clones.

Antibodies, Monoclonal↗
PubMed1986

The effectiveness of anti-Ia-immunotoxins in the suppression of MLR.

The potential use of a mouse anti-Ia monoclonal antibody conjugated with a plant toxin as an immunosuppressive agent for organ transplantation was examined by studying the mixed lymphocyte reaction (MLR). In initial observations in a murine system utilizing strains A/J and C57B1/6 (B6), it was shown that a rich-toxin-conjugated anti-I-Ek monoclonal antibody (13.4-immunotoxin) would kill Ia-bearing cells of strain A/J (I-Ek)--but not of strain B6, the cells of which lack I-E determinants. Studies reported here demonstrated that 13.4-immunotoxin effectively removed stimulatory cells from the I-E-bearing spleen cells but had no effect on spleen cells lacking I-E determinants or responder lymph node cells (I-E+ or I-E-) similarly treated (i.e., 1 microgram/10(6) cells). Taking advantage of the finding that such anti-I-E antibodies react with rat spleen cells bearing class II major histocompatibility complex molecules, we utilized these toxin-conjugated antibodies to inhibit MLR in rats. Assuming that the MLR is an in vitro representative of graft rejection, we suggest that such immunotoxins might be useful for pretreatment of organ allografts for transplantation across major histocompatibility barriers.

Animals↗
PubMed1986

Inhibition of rat mixed lymphocyte pancreatic islet cultures with anti-Ia immunotoxin.

Studies reported here indicate that an anti-Ia immunotoxin can eliminate the allostimulatory subpopulation of cells present within the islets of Langerhans without damaging the hormone-secreting cells. Such studies made use of an in vitro correlate of transplantation rejection, the mixed lymphocyte islet cell (MLIC) reaction. Using the MLIC, it was demonstrated that an anti-Ia immunotoxin removed cells capable of stimulating the MLIC in a dose-dependent fashion without altering the hormone-secreting functions of the remaining cells when challenged with glucose and theophylline. These studies suggest the feasibility of using such anti-Ia immunotoxins in islet allograft transplantation models to circumvent problems inherent in complement-mediated cytotoxicity, a previously documented effective form of inducing islet allotransplantation tolerance.

Animals↗
PubMed1986

One I region restriction determinant can associate with multiple antigenic epitopes.

Studies presented in this paper show that T cell clones recognizing different epitopes of multideterminant antigens can be restricted by the same I-A molecule. These data further support the concept that a single I-A restriction site can present more than one antigenic epitope. This concept was supported by data on the proliferation of T cell clones reactive with either poly(L-Glu60, L-Ala30, L-Tyr10)n(GAT) or poly(Tyr, Glu)-poly D,L-Ala--poly Lys [(T,G)-A--L] which recognized different epitopes on these multideterminant antigens. Two clones recognizing different epitopes on the same multideterminant antigen can be blocked by the same monoclonal anti-I-A antibody. Additionally, the mutation in the Abm12 chain utilized in [B6.C-H-2bm12(bm12) X B10.A(4R)]F1 mice can affect the restriction determinant of clones recognizing different antigenic epitopes. These results suggest that in the strictest sense, the determinant selection theory is not tenable and would support the concept that T cell specificity is controlled by the T cell repertoire.

Animals↗
PubMed1986

Gene conversion. A mechanism to explain HLA-D region and disease association.

In speculating about mechanisms that might give rise to T-cell epitopes appearing within different HLA-DR frameworks, we return to the hypothesis expressed above that suggests that gene-conversion-like events might be involved in shuffling the hypervariable segments of HLA-D region exons into alternative HLA-D region frameworks where they will still be recognized by the T cell (but not typed by conventional serology or mixed lymphocyte typing) as the "disease associated" HLA product. This might well explain the lack of stringent association between rheumatoid arthritis and HLA-DR4. It is possible, through the use of such alloreactive T-cell clones, that we might eventually define subgroups based upon presumed genetic susceptibility markers, which might allow therapeutic or prognostic assignment of patients with seropositive rheumatoid arthritis.

Arthritis, Rheumatoid↗
PubMed1986

Shared T cell recognition sites on human histocompatibility leukocyte antigen class II molecules of patients with seropositive rheumatoid arthritis.

Seropositive rheumatoid arthritis (RA) in adult and juvenile patients is associated with the serologic marker HLA-DR4. This association is incomplete; about one-third of the patients lack the disease-associated HLA-DR4 haplotype. The main biological function of class II molecules is to restrict the recognition of antigen by T lymphocytes. We therefore tested the hypothesis that patients with seropositive RA share T cell recognition sites for an unknown antigen and that such T cell "epitopes" are not identified by conventional serologic typing. We generated alloreactive human T cell clones by stimulating peripheral blood lymphocytes of normal donors against a lymphoblastoid cell line from a juvenile patient with seropositive RA. A panel of clones that recognized only HLA-Dw14 cells on a panel of homozygous typing cells was used to analyze class II molecules of adult patients with seropositive RA. By inhibition studies using monoclonal antibodies, the epitopes recognized by the different clones could be further characterized and assigned either to DR- or to DQ-encoded cell surface products. By using four different clones, it was possible to identify Dw14-associated T cell epitopes on all seropositive rheumatoid patients tested who typed HLA-DR4-positive and also on all eight DR4-negative patients tested. Approximately one-half of nonrheumatoid DR4-positive donors carried one or more determinants recognized by these clones; the expression of these allodeterminants in DR4-negative nonrheumatoid patients was rare (less than 10%). Thus, alloreactive human T cell clones are powerful tools to define T cell recognition sites on class II molecules that are not identified by conventional typing. Using T cell clones with specificities for determinants expressed on Dw14 homozygous typing lines, we were able to demonstrate shared epitopes on cells of all patients tested with seropositive RA irrespective of their HLA-D or HLA-DR type. These data suggest that major histocompatibility complex class II antigens of RA patients might be much more homogeneous than demonstrated by the incomplete HLA-DR4 association.

Arthritis, Rheumatoid↗
PubMed1986

IL 2 restores memory B cell activation by antigen-specific T cell clone variants.

It has recently been demonstrated that there are at least two separate pathways by which a single keyhole limpet hemocyanin (KLH) reactive T cell clone can induce B cell differentiation. With the use of the high-dose antigen-driven system (10 micrograms/ml trinitrophenyl (TNP)-KLH), a KLH-specific T cell clone was able to induce a primary anti-TNP response in unprimed B cells. In the presence of aliquots of the same T cell clone, a low-dose of antigen (5 X 10(-2) micrograms/ml TNP-KLH) induced an immunoglobulin (Ig)G response in primed B cells. It has also been demonstrated that there are variant subclones of such KLH-specific helper T cell clones that are unable to provide antigen-specific help in the presence of low-dose antigen but maintain the high-dose antigen-driven helper response. This study was undertaken to investigate whether interleukin 2 (IL 2) had some activity in the low-dose, antigen-driven response induced by the T cell clone. With the use of a variant T cell clone (which lost low-dose, antigen-driven helper activity), it was demonstrated that IL 2 was capable of reconstituting the low-dose, antigen-driven helper activity. To investigate whether accessory cells were required in this system, we removed the adherent cell population from the primed spleen cells added to culture. Interestingly, removal of the G10-adherent cells eliminated the low-dose, antigen-driven response induced by IL 2. Additionally by add-back experiments, we were able to demonstrate that the necessary adherent cell population did not require major histocompatibility complex (MHC) restriction for reconstitution of the IL 2-dependent, low-dose, antigen-driven response. Furthermore, 1% concanavalin A (Con A) supernatant (Sn), but not interleukin 1 (IL 1), could replace this adherent cell function. These data suggest that in this system, IL 2 bypasses the MHC-restricted interaction between T cells and antigen-charged adherent cells; B cells can present antigen to cloned helper T cells efficiently for primary responses but need an added factor(s) to induce IgG production; and adherent cells are essential for IgG production in primed B cells, possibly through the release of soluble factor(s) included in Con A Sn.

Animals↗
PubMed1986

Two independent pathways of helper activity provided by a single T cell clone.

Data presented in this paper demonstrate the existence of two separate pathways by which a single T cell clone can induce B cell differentiation. With the use of high doses of antigen, a T cell clone can induce a primary antibody response in unprimed B cells. With the use of low doses of antigen, the same T cell clone can induce an immunoglobulin (Ig)G response in primed B cells. The primary response is accompanied by T cell proliferation and lymphokine production (interleukin 2, B cell growth factor, B cell differentiation factor for immunoglobulin M, and B cell differentiation factor for immunoglobulin G). The secondary response does not require proliferation and occurs independently of detectable lymphokine production. Variants of the wild type T cell helper clone have been isolated. One variant can provide help to unprimed B cells when high doses of antigen are used. This variant cannot provide help to primed B cells when low doses of antigen are used, nor can it provide help to CBA/N "xid" B cells at any antigen concentration tested. Additional variants have been isolated that proliferate on antigen-pulsed-presenting cells, but fail to secrete detectable lymphokines and do not induce B cell differentiation. These results suggest that a single T cell helper clone has multiple functional activities that can be independently expressed.

Animals↗
PubMed1985

Human T cell clones express functional homing receptors required for normal lymphocyte trafficking.

To function efficiently in vivo, lymphocytes must circulate from the blood into lymphoid tissues and other sites of immune reaction. Herein, we show that human cytotoxic and helper T cell clones and lines, maintained in vitro with IL-2, express the functional capacity to recognize and bind to high endothelial venules (HEV), a capacity essential for lymphocyte exit from the blood, and hence for normal lymphocyte trafficking. The expression of functional homing receptors distinguishes human T cell clones from their murine counterparts, which uniformly lack receptors for HEV and are unable to migrate normally from the blood in vivo. The results raise the possibility that human T cell clones may be more effective in mediating in vivo immune responses than is suggested by murine models.

Appendix↗
PubMed1985

The effectiveness of anti-Ia-immunotoxins in the suppression of MLR.

The potential use of a mouse anti-Ia monoclonal antibody conjugated with a plant toxin as an immunosuppressive agent for organ transplantation was examined by studying the mixed lymphocyte reaction (MLR). In initial observations in a murine system utilizing strains A/J and C57B1/6 (B6), it was shown that a rich-toxin-conjugated anti-I-Ek monoclonal antibody (13.4-immunotoxin) would kill Ia-bearing cells of strain A/J (I-Ek)--but not of strain B6, the cells of which lack I-E determinants. Studies reported here demonstrated that 13.4-immunotoxin effectively removed stimulatory cells from the I-E-bearing spleen cells but had no effect on spleen cells lacking I-E determinants or responder lymph node cells (I-E+ or I-E-) similarly treated (i.e., 1 micrograms/10(6) cells). Taking advantage of the finding that such anti-I-E antibodies react with rat spleen cells bearing class II major histocompatibility complex molecules, we utilized these toxin-conjugated antibodies to inhibit MLR in rats. Assuming that the MLR is an in vitro representative of graft rejection, we suggest that such immunotoxins might be useful for pretreatment of organ allografts for transplantation across major histocompatibility barriers.

Animals↗
PubMed1985

Interferon gamma production by herpes simplex virus antigen-specific T cell clones from patients with recurrent herpes labialis.

Nineteen herpes simplex virus (HSV) antigen-specific human T lymphocyte clones were established from three volunteers with recent recurrent herpes labialis. All produced interferon gamma (IFN-gamma) at titres of 200 to 700 units/ml when cultured in vitro with HSV antigen and irradiated peripheral blood mononuclear cells (PBMC) as filler cells. All 10 of those clones whose phenotype was determined were Leu 4+, Leu 2-, Leu 3+. Interleukin 2 alone failed to induce IFN-gamma in titres greater than 10 units/ml from these clones cultured at 10(4)/0.2 ml/well. However, the effect of different accessory or filler cells on IFN-gamma production by clones was quite marked. For example, high titres were produced when irradiated PBMC or plastic-adherent cells (predominantly monocytes) were added and low titres when macrophages and irradiated Epstein-Barr virus-transformed B (EBV-B) cells were added. When tested for HSV antigen-stimulated IFN production alone, the irradiated PBMC and adherent cells produced low titres, but no detectable interferon was produced by the others. However, with higher concentrations of EBV-B cells, low concentrations of IFN-alpha were occasionally produced. Irradiation strikingly reduced IFN-alpha-production by PBMC. The IFN-alpha and -gamma produced by accessory cells may contribute to total IFN production by priming the production by cloned cells, and acting in synergy with IFN-gamma produced by the cloned cells. Alternatively, the effect may be due to the presence of permissive concentrations of other lymphokines such as the interleukins. Interferon production by cloned T lymphocytes in the presence of non-producing macrophages was maximal within 24 h, much faster than with a similar polyclonal system, although attaining lower titres. EBV-B cells from only one of three patients supported antigen-specific lymphocyte activation. Almost all cells of the three cell lines expressed DR antigens, while DS/DC antigens were also expressed on nearly all cells of the antigen-presenting line and, at lower densities, on two-thirds of the cells of the other two lines.

Antigen-Presenting Cells↗
PubMed1985

An analysis of monoclonal T cell and antibody recognition sites on Ia molecules.

The advances made in understanding T cell and antibody recognition sites on Ia using monoclonal helper and alloreactive T cells are summarized. For many antibodies it has been possible to determine whether the antibody recognition site was determined by the alpha or beta chain. Such defined antibody reagents have allowed the definition of multiple functional antigen presenting sites on a given Ia molecule. Mutant antigen-presenting cells independently suggest the existence of such multiple functional sites. A detailed analysis of the I-Ab mutant bm 12 directly defines the chemical nature of one such site and suggests that it arose as a result of gene conversion. Such regions of Ia molecules may be important for both T-cell function and antibody-binding.

Animals↗
PubMed1985

Type II collagen-reactive T cell clones from mice with collagen-induced arthritis.

Certain strains of mice develop a symmetrical polyarthritis after immunization with type II collagen. The incidence of arthritis after such immunization is variable. To study the arthritogenic potential of T cells reactive with type II collagen, we isolated draining lymph node cells from mice that had developed arthritis after immunization with bovine type II collagen. From these immune lymph node cells we were able to clone T cells reactive with type II collagen. Two separate sets of T cell clones were isolated. The first set reacted with either native bovine or native chick type II collagen, but did not react with type I collagen. The second set of T cell clones reacted with bovine type II collagen, but did not respond to either native chick type II collagen or type I collagen. These clones will be tested for their influence on the development of arthritis in vivo.

Animals↗