Biomedical subjects

M J Irwin

Publications and source records attributed to M J Irwin.

17 recordsLinked to original sources

PubMed1994

Direct injection of a recombinant retroviral vector induces human immunodeficiency virus-specific immune responses in mice and nonhuman primates.

The cytotoxic T-lymphocyte (CTL) response plays an important role in controlling the severity and duration of viral infections. Immunization by direct in vivo administration of retroviral vector particles represents an efficient means of introducing and expressing genes and, subsequently, the proteins they encode in vivo in mammalian cells. In this manner foreign proteins can be provided to the endogenous, class I major histocompatibility complex antigen presentation pathway leading to CTL activation. A nonreplicating recombinant retroviral vector, encoding the human immunodeficiency virus type 1 (HIV-1) IIIB envelope and rev proteins, has been developed and examined for stimulation of immune responses in mouse, rhesus macaque, and baboon models. Animals were immunized by direct intramuscular injection of the retroviral vector particles. Vector-immunized mice, macaques, and baboons generated long-lived CD8+, major histocompatibility complex-restricted CTL responses that were HIV-1 protein specific. The CTL responses were found to be dependent on the ability of the retroviral vector to transduce cells. The vector also elicited HIV-1 envelope-specific antibody responses in mice and baboons. These studies demonstrate the ability of a retroviral vector encoding HIV-1 proteins to stimulate cellular and humoral immune responses and suggest that retrovector immunization may provide an effective means of inducing or augmenting CTL responses in HIV-1-infected individuals.

Animals↗

PubMed1993

Interplay between superantigens and the immune system.

Superantigens interact with the immune system by binding to major histocompatibility complex (MHC) class II proteins and activating T cells through the variable region of the T cell receptor beta-chain. Through this means they can cause massive proliferation and then death of a large proportion of T cells. Superantigens are produced by bacteria, mycoplasmas, retroviruses, and probably by other organisms. In some cases, the superantigen is crucial to the organism's life cycle. Mouse mammary tumor virus disseminates by activating T cells which stimulate the proliferation of B cells harboring the virus. In other cases, the superantigen may be responsible for the pathogenesis of the infection, such as in the case of Toxic Shock Syndrome. In this article, we review information on the diseases in which superantigens are involved, and the mechanisms by which the superantigens interact with T cell receptor and class II molecules.

Animals↗

PubMed1993

T-cell receptor beta-chain binding to enterotoxin superantigens.

The last few years have seen an enormous jump in our knowledge and understanding of T-cell activation by superantigens. Clearly, a great number of infectious and parasitic organisms utilize superantigens as part of a strategy to evade the immune response of their host. The ability to modulate superantigen effects will give us new means to fight infections, and the knowledge of T-cell activation that we have gained from study of superantigens will, in turn, allow us to modulate the immune system in new ways.

Animals↗

PubMed1992

Selecting T cell receptors with high affinity for self-MHC by decreasing the contribution of CD8.

Selective events during T cell repertoire development in the thymus include both the positive selection of cells whose receptors recognize self-major histocompatibility complex (MHC) molecules and negative selection (tolerance) of cells whose interaction with self-MHC is of high affinity. The affinity of T cell interactions with class I MHC molecules includes contributions by both the T cell receptor and the CD8 coreceptor. Therefore, by decreasing the affinity of the interaction with CD8, T cells whose receptors have relatively high affinities for self-MHC may survive negative selection. Such T cells were generated and those T cells reactive with self-MHC plus antigen also displayed low affinity for self.

Animals↗

PubMed1992

Enterotoxin residues determining T-cell receptor V beta binding specificity.

Superantigens such as the staphylococcal enterotoxins bind to major histocompatibility complex (MHC) class II molecules and activate T cells through a specific interaction between the V beta region of the T-cell antigen receptor (TCR) and the toxin. The TCR beta-chain alone is sufficient to produce the interaction with the enterotoxin-class II complex. Identification of the regions of enterotoxins that interact with TCR has so far proved equivocal because of difficulties in distinguishing between direct effects on T-cell recognition and indirect effects resulting from alteration of binding to class II. For example, amino-terminal truncations of SEB abrogated T-cell stimulation whereas carboxy-terminal truncation of SEA stopped its mitogenic activity. The most comprehensive study to date, accounting for both enterotoxin binding to class II and enterotoxin interactions with the TCR, identified two functionally important regions for SEB binding to TCR. Although the amino-acid sequences of staphylococcal enterotoxins A and E are 82% identical, they activate T cells bearing different V beta elements. We have assayed the binding of cells coated with these enterotoxins to soluble secreted TCR beta-chain protein and find that V beta 3 binds enterotoxin A but not E, whereas V beta 11 binds enterotoxin but not A. To map the amino-acid residues responsible for these different binding specificities, we prepared a series of hybrids between the two staphylococcal enterotoxins. We report that just two amino-acid residues near the carboxy terminus of the enterotoxins are responsible for the discrimination between these molecules by V beta 3 and V beta 11.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1992

T-cell antigen receptor binding sites for the microbial superantigen staphylococcal enterotoxin A.

We have examined the interaction of the microbial superantigen staphylococcal enterotoxin A (SEA) with peptides corresponding to overlapping regions of the T-cell antigen receptor beta chain variable region V beta 3. SEA is known to stimulate murine T cells bearing certain V beta elements, among them V beta 3. Five peptides were synthesized representing amino acids 1-24, 20-44, 39-60, 57-77, and 74-95 of V beta 3. We demonstrate here that soluble V beta 3-bearing beta chains can bind to a complex of SEA and major histocompatibility complex class II and that the synthetic peptide V beta 3-(57-77) blocked this interaction. The peptide V beta 3-(57-77) also inhibited SEA-induced interferon-gamma production and SEA-induced proliferation of B10.BR spleen cells. Conversely, the peptide corresponding to amino acids 57-77 of V beta 8.2, a V beta element that is not recognized by SEA, decreased staphylococcal enterotoxin C-2-induced proliferation but did not affect SEA-induced proliferation. The peptide inhibition of SEA-induced function was due at least in part to inhibition of V beta 3-bearing T-cell activity, since the percentage of T cells reactive with an anti-V beta 3 monoclonal antibody was significantly reduced by V beta 3-(57-77). These data suggest that the region of V beta 3 encompassing amino acids 57-77 is an area that displays the appropriate sequence and conformation for binding of the SEA molecule and blocking of the resultant interaction with the T-cell antigen receptor.

Amino Acid Sequence↗

PubMed1989

Species-restricted interactions between CD8 and the alpha 3 domain of class I influence the magnitude of the xenogeneic response.

As compared with the vigorous T cell response normally observed against allogeneic MHC molecules, T cells recognize xenogeneic MHC molecules poorly. To define structural features of the MHC molecule important for such species-specific recognition, HLA-A2(A2)-specific murine CTL were examined for their recognition of transfected cell lines expressing the class I molecules A2 or A2/H-2Kb(A2/Kb). A2/Kb is a chimeric molecule consisting of the alpha 1 and alpha 2 domains of A2 and the alpha 3, transmembrane, and cytoplasmic regions of Kb. The majority of CTL clones showed enhanced recognition of transfected cell lines expressing this chimeric molecule. Enhanced recognition was shown to correlate with sensitivity of the CTL clones to inhibition by anti-CD8 antibody. These results suggested that CD8 may interact with class I in a species-specific manner, and that suboptimal CD8 interaction with the alpha 3 domain of xenogeneic molecules may be an important contribution to poor xenoreactivity. This conclusion was supported by the capacity of A2/Kb, but not A2 human cell transfectants, to induce a primary in vitro CTL xenoresponse specific for A2.

Animals↗

PubMed1986

Primary in vitro stimulation of antibody production by rainbow trout lymphocytes.

Trinitrophenylated (TNP) forms of E. coli lipopolysaccharide (LPS) and keyhole limpet hemocyanin (KLH) were used to produce antigen specific plaque-forming cell (PFC) responses with rainbow trout (Salmo gairdneri) splenocytes from unprimed fish in vitro. The culture system that was developed is described and characterized with respect to the kinetics and dose responses for both the haptenated and unhaptenated forms of the carriers. The induction of the PFC response to TNP-LPS was inhibited with TNP-lysine. Exposure to graded levels of gamma-radiation demonstrated a low dose augmentation of the PFC response with both antigens. Antigen addition experiments reveal that both antigens appear to stimulate the same population of antibody-producing B lymphocytes.

Animals↗

PubMed1986

Salmonid B lymphocytes demonstrate organ dependent functional heterogeneity.

The passive hemolytic plaque assay was used to examine the functional heterogeneity of antibody producing cells in salmonid immune organs. In this study, the antibody response to Vibrio anguillarum antigens was induced by the injection of a somatic antigen extract. This antigen was also coated onto sheep red blood cells (SRBC) for plaque forming cell (PFC) determination. Previous studies have demonstrated that this response is antibody dependent and antigen specific (Kaattari and Irwin, 1985). The present study was focused upon the heterogeneity of antibody producing cells that arise in the spleen, anterior and posterior kidney of immunized coho salmon (Oncorhynchus kisutch). The functional heterogeneity of lymphocytes was assessed by histogram analysis of the antigen inhibition profiles of the plaque forming responses. These analyses have revealed that the anterior kidney lymphocytes possess a much more restricted profile of antibody specificities than do lymphocytes from the posterior kidney or spleen. These data suggest that B cell repetoires differ among the immune organs of salmonids.

Animals↗

PubMed1985

Salmonid spleen and anterior kidney harbor populations of lymphocytes with different B cell repertoires.

An O-antigen extract of the fish pathogen Vibrio anguillarum was used to stimulate plaque-forming cells (PFC) in coho salmon. The kinetics of the response demonstrates peak PFC per organ on day 16 post immunization for the spleen and anterior kidney. Significant PFC were also seen in thymic tissue. PFC responses were shown to be immunoglobulin mediated and antigen specific. Inhibition profiles of responding PFC populations demonstrate that the cells of the anterior kidney are more restricted in their recognition of antigen than those of the spleen. These data lend functional support to the concept of the hematopoietic nature of the anterior kidney of teleosts.

Animals↗

PubMed1983

Stoichiometric characteristics and resonance Raman spectra of azidosemimethemerythrin.

With extra precautions to remove dissolved oxygen, reduction of aquomethemerythrin with dithionite occurs with a stoichiometry very close to 1.0. The aquosemimethemerythrin so produced combines with N3- ion almost on a 1:1 basis per monomer. Resonance Raman spectra of azidosemimethemerythrin differ from those of azidomethemerythrin in the position of the Fe-N stretching frequency and in the absence of a feature corresponding to a mu-oxo bridge, but in both complexes the internal azide stretch occurs at the same frequency and the substitution of isotopically unsymmetrical 15N14N-2 leads to a splitting of the Fe-N band. These observations provide some insight into the structural features of the binuclear functional site.

Animals↗

PubMed1983

Oxidation state of binuclear iron site in azidosemimethemerythrin.

Electron paramagnetic resonance spectra of azidosemimethemerythrin (from Phascolopsis gouldii) have been integrated to find the total number of spins per monomer unit. The value observed, 1.0 +/- 0.1 spins per Fe2 pair, confirms the assignment of a hybrid oxidation state, FeIIFeIII, to each site.

Animals↗

PubMed1981