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W L Havran

Publications and source records attributed to W L Havran.

At least 37 records · Page 2Linked to original sources
PubMed1991

Recognition of self antigens by skin-derived T cells with invariant gamma delta antigen receptors.

Thy-1+ dendritic epidermal T cells (dECs) express invariant gamma delta antigen receptors and are found in intimate contact with keratinocytes in murine epidermis--thus raising the possibility that keratinocytes express a ligand for the antigen receptor of these T cells. Thy-1+ dECs were stimulated to produce lymphokines by interaction with keratinocytes in vitro. This stimulation was mediated through the dEC antigen receptor and did not appear to be restricted by the major histocompatibility complex. Thus, dECs can recognize self antigens and may participate in immune surveillance for cellular damage rather than for foreign antigens.

Animals↗
PubMed1991

Gamma delta T cells in murine epithelia: origin, repertoire, and function.

The earliest TCR+ cells to appear during fetal development express products of the gamma and delta loci, and emerge as successive waves of cells bearing different V gamma gene products. These appear to emigrate and seed different epithelia. The TCR repertoire of the first two of these waves, V gamma 3 and V gamma 4, respectively, is extremely restricted. Whether the repertoire of these cells is restricted by selective processes or is shaped by developmental restrictions on rearrangements remains to be determined. These cells may function in surveillance for signals of trauma by recognizing self products induced by cellular stress.

Animals↗
PubMed1991

The immunobiology of T cells with invariant gamma delta antigen receptors.

T cells bearing specific gamma delta TCR are the major lymphoid population in certain epithelial tissues. There are striking differences between these and peripheral T cells. The epithelial gamma delta T cells exhibit highly restricted V gene use, preferential pairing of TCR chains, and lack of diversity at the junctions creating populations of cells with virtually identical TCR in particular epithelia. Generation of certain epithelial gamma delta populations appears to be restricted to a discrete stage early in development. The restricted localization and expression of invariant antigen receptors may equip the epithelial gamma delta T cells to perform specialized functions which differ from those of circulating alpha beta and gamma delta TCR+ cells. This review provides a summary of the characterization of gamma delta T cells found in epithelial tissues and speculates on the in vivo role of these cells.

Amino Acid Sequence↗
PubMed1991

Murine T cells with invariant gamma delta antigen receptors: origin, repertoire, and specificity.

T cells bearing invariant gamma delta T cell antigen receptors localize to distinct epithelial sites in the adult mouse. These gamma delta T cells differ from the lymphoid alpha beta and gamma delta T cells in several ways. The epithelial gamma delta T cells appear to be the product of the earliest waves of TCR expressing cells in the fetal thymus. Additionally, the rearranged TCR junctions exhibit a distinct lack of diversity, possibly a result of the fetal origin and a specialized selection process. The use of a single invariant TCR and strict tissue localization suggest that these gamma delta T cells may provide a specialized function in the epithelial tissues distinct from that of the circulating alpha beta and gamma delta T cells.

Animals↗
PubMed1990

Origin of Thy-1+ dendritic epidermal cells of adult mice from fetal thymic precursors.

The skin of mice contains dendritic epidermal cells carrying the Thy-1 antigen (Thy-1+ dEC) which express antigen receptors composed of the T-cell antigen receptor (TCR) gamma- and delta-chains. Although the role of the thymus in the generation of most T cells is well established, the involvement of the thymus in the generation of Thy-1+ dEC is not clear. Because bone marrow cells can give rise in Thy-1+ dEC in chimaeric mice and Thy-1+ dEC are detected in the skin of athymic nude nice, it has been proposed that Thy-1+ dEC arise continuously from bone marrow precursors by a thymus-independent mechanism. But it has recently been determined that Thy-1+ dEC in nude mice do not express TCR at the cell surface, and that the gamma- and delta-chain genes are in germ-line configuration, leaving the role of the thymus in the generation of Thy-1+ dEC uncertain. Most Thy-1+ dEC in all normal mouse strains examined express TCR containing the V gamma 3 gene product. This V gene segment is expressed on the first wave of TCR-expressing cells to emerge during fetal development, and in adult mice is detectable only on cells in the epidermis. In addition to use of this 'fetal' V gamma segment, other features of the Thy-1+ dEC TCR genes, including absence or minimal presence of nongerm-line-encoded nucleotides at the junctions and use of a single D element in the rearranged delta-chain gene are typical of rearrangements found in fetal, and not adult, thymus. Here we demonstrate that precursors that are present only in the fetal thymus give rise to Thy-1+ dEC in the skin of adult mice.

Animals↗
PubMed1989

Phenotypic and functional analysis of gamma delta T cell receptor-positive murine dendritic epidermal clones.

Thy-1+ dendritic cells isolated from the epidermis of normal mice (dEC)3 bear the gamma delta TCR associated with the CD3 complex. We have analyzed the effects of antibodies directed against the TCR complex, Ly-6C, and Thy-1, as well as pharmacologic agents which have been shown to activate T cells without engagement of the TCR complex, on levels of intracellular free calcium, activation of protein kinase C, cytolysis, IL-2R expression, and secretion of lymphokines by dEC clones. We have found that the dEC cells express a fully functional TCR complex which can function to transmit signals upon perturbation leading to an increase in IL-2R expression, release of lymphokines, and cytolytic activity. These results indicate that the gamma delta TCR+ dEC are capable of responding to activation signals in the same manner as mature alpha beta TCR+ cells and suggests that they may play a functional role in the skin.

Animals↗
PubMed1989

Limited diversity of T-cell receptor gamma-chain expression of murine Thy-1+ dendritic epidermal cells revealed by V gamma 3-specific monoclonal antibody.

To study the origin of and the degree of T-cell antigen receptor (TCR) diversity of Thy-1+ dendritic epidermal cells (Thy-1+ dECs) in mice, we have developed a monoclonal antibody (mAb 536) to the gamma delta TCR. mAb 536 binds to and stimulates interleukin 2 secretion from Thy-1+ dEC but not cells that express TCR composed of alpha and beta chains. mAb 536 precipitates CD3-associated gamma and delta chains from lysates of radioiodinated Thy-1+ dECs. Analysis of a panel of hybridomas that express gamma delta TCR indicated that mAb 536 defines an epitope of the variable region (V gamma 3) gene product. Flow cytometric analysis revealed that expression of V gamma 3 in the adult mouse is restricted to cells in the epidermis, where essentially all Thy-1+ cells are V gamma 3+. The majority of CD3+ cells in the 14-day fetal thymus also express V gamma 3. These results indicate that the T-cell complement in epidermis are cells that express gamma delta TCR and that the diversity of antigens recognized by the cells might be restricted by the use of a single V gamma gene segment. Finally, the data raise the intriguing possibility that Thy-1+ dECs may arise from precursors that are among the first to emerge from the developing thymus. This suggests that V gene usage during thymocyte development is highly regulated and has important consequences on the tissue localization and function of the emerging cells. As in other developing tissues, it appears that programmed and transient gene expression determines the fate of the emerging cells.

Animals↗
PubMed1988

Developmentally ordered appearance of thymocytes expressing different T-cell antigen receptors.

The T-cell repertoire is elaborated by a still poorly understood process during which precursor cells arising in the bone marrow seed the thymus to provide a starting point for intrathymic differentiation and selection. The products of the process are cells which express antigen receptors composed of either alpha/beta or gamma/delta heterodimers in association with CD3. The finding that the appearance of T-cell antigen receptor gamma- and delta-gene rearrangements and transcripts precedes those of full-length beta- and alpha-transcripts during ontogeny indicates that the process is ordered, a conclusion supported by the fact that the appearance of thymocytes expressing CD3-associated gamma/delta heterodimers precedes the appearance of those bearing alpha/beta heterodimers. The recent demonstrations that within the gamma- and delta-loci there is ordered and sometimes transient rearrangement and expression of specific V delta and V gamma gene segments during ontogeny raised the possibility that qualitative changes in the capacity of the differentiative process to generate components of the T-cell armamentarium might occur. We have produced a monoclonal antibody that detects an epitope of the V gamma 3 gene product, a gene segment expressed only in the early fetal thymus. In this report we demonstrate that cells expressing V gamma 3 are present transiently at the earliest stages of thymocyte development, preceding the appearance of cells bearing other gamma/delta or alpha/beta receptors. In the adult mouse, V gamma 3 expression appears to be limited to Thy-1+ cells in the epidermis. These results suggest a profound programming and staging in elaboration of the components of the T-cell system during the early stages of thymocyte development in the embryo.

Animals↗
PubMed1988

Effects of anti-Lyt-2 and anti-L3T4 monoclonal antibodies on the function of cytotoxic T lymphocyte/helper T lymphocyte hybrid T cell clones.

CTL/HTL hybrid clones provide a unique system that allows detailed analysis of the role of Lyt-2, L3T4, and other structures involved in T cell functions. We have demonstrated previously that the fusion of cloned murine CTL and helper T lymphocytes with defined specificity generated hybrid cells that expressed both Lyt-2 and L3T4 as well as two TCR. Data obtained with these hybrid clones demonstrated that cytolysis is closely linked to the CTL TCR. We have analyzed the effects of anti-Lyt-2 and anti-L3T4 as well as anti-TCR mAb on cytolysis, proliferation, and lymphokine release by a number of hybrid clones. We found that anti-Lyt-2 and anti-L3T4 mAb were able to inhibit both proliferation and lymphokine release by the hybrid clones in response to stimulation of either the CTL or helper T lymphocyte parent TCR. In contrast, only anti-Lyt-2 and anti-CTL TCR mAb were able to block cytolysis of target cells bearing the Ag recognized by the CTL TCR. These results provide further evidence that cytolysis is closely linked to the CTL TCR and that Lyt-2 and L3T4 have more than a passive role as accessory molecules on the surface of T lymphocytes.

Animals↗
PubMed1988

Characterization of an anti-Ly-6 monoclonal antibody which defines and activates cytolytic T lymphocytes.

HK1.4 mAb was identified based on its ability to stimulate proliferation of cloned murine CTL. Within the lymphoid lineage, mAb HK1.4 bound exclusively to CTL, regardless of the expression of Lyt-2 or MHC restriction. HK1.4 mAb also bound to 40% of bone marrow cells and less than 5% of thymocytes from all mouse strains tested. Based on the tissue distribution of the determinant with which it reacted and the ability to cross-block binding of the anti-Ly-6 mAb H9/25, mAb HK1.4 appeared to react with a product of the Ly-6 locus. However, significant differences were observed between the properties of mAb HK1.4 and other, previously described anti-Ly-6 mAb. Cell proliferation and lymphokine release by cloned CTL were stimulated by culture with mAb HK1.4 alone or in the presence of non-stimulatory levels of IL-2. This proliferation and lymphokine release were not blocked by the addition of soluble anti-Lyt-2 or anti-IL-2R mAb. Activation induced by HK1.4 mAb proceeds in the absence of accessory cells, of cross-linking of the TCR, or the addition of mitogens or PMA. Stimulation of cells by anti-TCR mAb was not blocked by the addition of soluble HK1.4 mAb, and the stimulatory effects of HK1.4 and anti-TCR mAb were not additive. However, IL-2-driven proliferation of CTL clones was dramatically inhibited by the addition of HK1.4 mAb.HK1.4 mAb had no effect on Ag-specific or lectin-facilitated cytolysis. Taken together, these data indicate that mAb HK1.4 operates via an IL-2-independent pathway of activation that is also independent of the TCR.

Animals↗
PubMed1987

Antibodies to the L3T4 and Lyt-2 molecules interfere with antigen receptor-driven activation of cloned murine T cells.

When L3T4+ cloned murine helper T lymphocytes (HTL) are stimulated with antigen or immobilized anti-T cell receptor (TCR) monoclonal antibodies (mAb) at concentrations which are optimal for proliferation, anti-L3T4 mAb inhibits activation as measured by proliferation and lymphokine production. Under similar conditions, IL 2-independent proliferation of Lyt-2+ cloned murine cytolytic T lymphocytes (CTL) stimulated by anti-TCR mAb is inhibited by anti-Lyt-2 antibodies. Proliferation of cloned HTL and CTL cells stimulated by IL 2 is not affected by the anti-L3T4 and anti-Lyt-2 mAb. The inhibition of TCR-induced activation of the T cell clones is not due to interference with the binding of the anti-TCR mAb. Stimulation of the TCR has been proposed to induce lymphokine secretion and proliferation by T cells through a pathway involving the activation of protein kinase C and the stimulation of an increase in the concentration of intracellular free calcium. However, proliferation of T cells stimulated by PMA (which activates protein kinase C) plus the calcium ionophore A23187 (which increases the concentration of intracellular free calcium) is not affected by mAb reactive with the Lyt-2 or L3T4 structures. If TCR stimulation does indeed activate T cells by activating protein kinase and increasing intracellular free calcium, then our data suggest that anti-L3T4 and anti-Lyt-2 mAb inhibit TCR-driven proliferation at some step before the activation of protein kinase C and the stimulation of a rise in intracellular free calcium concentration. Our results suggest that anti-L3T4 and anti-Lyt-2 mAb interfere with early biochemical processes induced by stimulation of the TCR. In HTL, which proliferate via an autocrine pathway, anti-L3T4 mAb appears to inhibit proliferation by interfering with signaling events involved in lymphokine production. Inhibition of IL 2-independent proliferation of Lyt-2+ cells by anti-Lyt-2 mAb appears to occur by a different mechanism. The precise molecular basis for the interference of each cell type has not yet been characterized.

Animals↗
PubMed1986

Interleukin-2 differentially regulates IL-2 receptors on murine cloned cytolytic and helper T cells.

The effects of interleukin-2 (IL-2) on the expression of IL-2 receptors by cloned cytolytic and helper T lymphocytes were studied using three anti-IL-2 receptor antibodies. IL-2 enhanced the expression of IL-2 receptors on all clones tested. A steep dose-response curve was observed with no measurable effect seen below 2 units/ml and maximal IL-2 receptor expression with greater than 5 units/ml. IL-2 receptor expression peaked 24-48 hr after the addition of IL-2. The subsequent decrease in IL-2 receptor expression correlated with a decrease in the levels of IL-2 remaining in the culture supernatants of cytolytic T lymphocyte cells. Removing residual IL-2 from cultures resulted in the rapid return of IL-2 receptor expression to unstimulated levels. The daily addition of low levels of IL-2 to cultures resulted in the prolonged expression of high levels of IL-2 receptors by non-IL-2-producing cloned cytolytic T cells. Cloned helper T cells which make IL-2 showed the initial increase in IL-2 receptor levels, but the daily addition of IL-2 did not prolong IL-2 receptor expression in these cells. These data suggest that IL-2 receptors on those cells which do not make IL-2 are regulated differently from receptors on cells which themselves make IL-2.

Animals↗
PubMed1984

Cell surface structures involved in T cell activation.

We have discussed four specific models which provide different kinds of information about the requirements for T cell activation. The first utilized a CTL clone designated L3, which is reactive specifically with Ld alloantigen, to study the involvement of the associative recognition structure Lyt-2 in cytolysis. The apparent requirements for activation of this CTL clone differ depending on whether the target cells bear specific alloantigen or are hybridoma cells which express on their cell surface a clonotypic antibody which reacts specifically with the L3 T cell receptor for antigen. When the antigen receptor reacts with alloantigen on the allogeneic target cell, cytolysis is inhibited by anti-Lyt-2 antibody. However, when the clonotypic antibody of the target cell reacts with the antigen receptor of the T cell, cytolysis is much less inhibited by anti-Lyt-2 antibody. The antigen receptor seems to be responsible for the specificity of both these interactions but the avidity of the interaction between CTL and target cell seems to differ in the two situations. Evidence that participation of the L3T4 associative recognition structure on HTL is less important for cloned T cells which have higher affinity antigen receptors was provided by the second model system which used cloned HTL selected for optimal responses to different concentrations of nominal antigen. Proliferative responses of those clones which responded to lower antigen concentrations were less readily inhibited by anti-L3T4 mAb. Evidence provided by these two model systems is consistent with the concept that associative recognition structures are of lesser importance for T cell activation for those T cells which have higher affinity antigen receptors. In the third model system, we have identified several monoclonal antibodies which augment proliferative response of cloned T cells to sub-optimal amounts of IL-2, probably by reacting with the antigen receptor or with the associated Leu-4/T3 structure. The reactivity patterns of these antibodies indicate that several different epitopes are being recognized. Some appear to be clonotypic although they do not block functional activity of the clone with which they react. Others react with all T clones which we have tested. Several of these react with a cell surface antigen which is expressed at about the same level as the clonotypic structures: these antibodies may react with the murine equivalent of the human Leu-4/T3 molecular complex. One of the "pan-T cell" antibodies which augments IL-2-induced T cell proliferation appears to react with Thy-1; this antibody is similar to one described recently by Gunter et al. (1984).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

mIgM:mIgD ratios on B cells: mean mIgD expression exceeds mIgM by 10-fold on most splenic B cells.

The relative frequency of mIgM and mIgD molecules on B cell surfaces is important in determining, in large part, the isotype involvement in antigen binding and signal transduction. Although it is generally assumed that on most mature B cells, mIgM and mIgD occur in roughly equal quantities, no formal analysis of this question has been reported. In this report, we describe such an analysis based on the quantitation of anti-Fab or anti-kappa specific immunofluorescence of splenic B cells before or after capping with rabbit anti-IgD or anti-IgM antibodies or both. The results indicate that, whereas mean expression of IgD exceeds IgM on splenocytes by threefold, members of the major B cell subpopulation (60 to 70% of cells) express 10-fold more IgD than IgM.

Animals↗
PubMed1983

B lymphocyte activation: entry into cell cycle is accompanied by decreased expression of IgD but not IgM.

To gain insight into the function of cell surface IgM (sIgM) and IgD (sIgD), the expression of these markers on B lymphocytes was quantitated during activation and progression through the cell cycle. Specifically, analysis and correlation of changes in cell cycle state, sIgM and sIgD expression and cell size following exposure of murine B cells to mitogenic levels of lipopolysaccharide and dextran sulfate is reported. As assessed by flow cytometric acridine orange analysis, a large proportion of normal splenic B cells respond within 48 h of exposure to these mitogens by entry into the cell cycle. This response is accompanied by an increase in cell size as determined by flow cytometric "time of flight" measurement. Flow cytometric immunofluorescence analysis reveals a simultaneous alteration in sIg expression. Specifically, cells leaving G0 and transiting G1 increase in diameter from 5 microns to 6 microns and lose greater than 80% of sIgD while sIgM remains constant. Progression through the remainder of the cell cycle is accompanied by a further increase in mean cell diameter to approximately 12 microns while sIgM and sIgD levels remain at G1 levels. The abrupt loss of sIgD as cells transit G1 suggests that an active process mediates this decrease.

Animals↗
PubMed1982

Enrichment of viable lymphocytes in defined cycle phases by sorting on the basis of pulse width of axial light extinction.

A correlation between cell size and cycle state is demonstrated for mitogen stimulated murine lymphocytes. Cell cycle analysis was performed using multiparameter cytofluorometric analysis of acridine orange stained cells. Cell size was determined by measuring "time of flight" of axial light extinction. Cells with diameters of 5.0 - 6.0 micron are shown to be predominately in G0. Among stimulated cells, those 6.0 - 7.0 micron in diameter are predominately early and late G1 (80%) with some S phase cells. Cells in G2 + M were found to predominate among lymphocytes with diameters of 7.5 - 12 micron. This approach provides a method for isolation of lymphocytes in specific phases of the cell cycle which are suitable for subsequent functional studies.

Acridine Orange↗