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D W Scott

Publications and source records attributed to D W Scott.

At least 199 records · Page 11Linked to original sources
PubMed1982

Effect of recent antigen exposure on the functional expression of B cell subpopulations.

We investigated whether the definition of functional B cell subpopulations changes after the exposure of B cells to specific antigen. Recent in vivo priming with fluorescein- (FL) coupled T-independent (TI) antigens leads to an augmentation of the subsequent in vitro responses of B cells to FL-coupled TI antigens, including FL-polymerized flagellin, FL-lipopolysaccharide, and FL-Brucella abortus, as well as a FL-coupled T-dependent (TD) antigen, FL-keyhole limpet hemocyanin (KLH). This effect, which is evident 7 days after priming, is of short duration in that B cells from FL-Ficoll injected mice display normal responsiveness 3 wk after priming. When mice are primed with FL-KLH, the TD antigen, B cells responsive to a subsequent FL-KLH challenge are expanded, but not short-term cross-priming for any of the TI antigen challenges is observed. Limiting dilution precursor analysis shows that B cell populations responding to different FL-coupled TD and TI antigens overlap in unimmunized animals. FL-TI antigen priming induces not only quantitative changes in the responding B cells (increased precursor frequencies) but also results in functional changes in FL-specific B cells. The primed B cells now respond to FL-hapten in a carrier-restricted manner and behave as independent (non-overlapping) subpopulations. We suggest that B cell responses to different forms of the same hapten are influenced in part by their recent "history" of antigenic exposure.

Animals↗
PubMed1981

Pemphigus and pemphigoid in dog and man: comparative aspects.

A review of canine pemphigus vulgaris, pemphigus vegetans, pemphigus foliaceus, pemphigus erythematosus, and bullous pemphigoid shows them to share many clinicopathologic similarities with their human counterparts. Because of their numerous analogies in clinical presentations, histopathologic and immunopathologic findings, and therapeutic results, canine and human pemphigus and pemphigoid may represent a valuable area for comparative dermatologic research.

Animals↗
PubMed1981

Hapten-specific murine colony-forming B cells: in vitro response of colonies to fluoresceinated thymus independent antigens.

The ability to clone hapten-specific B cells in agar and to subsequently trigger their clonal progeny to antibody synthesis was investigated. Fluorescein (FL) specific B cells were purified on FL-gelatin dishes and cultured in semisolid agar for 6 to 7 days; individual colonies were then picked for restimulation in microculture. FL-specific B cells could be cloned as efficiently as unpurified splenic B cells. The number of colonies formed depended on the presence of sheep erythrocytes (SRBC) or E. coli lipopolysaccharide (LPS) in the cultures. An additive number of colonies were observed with SRBC + LPS compared to that of SRBC or LPS alone. The colonies obtained from SRBC-containing cultures were stimulatable at high frequency by various FL-conjugated antigens to yield anti-FL PFC. However, colonies grown with LPS as the only additive were not stimulatable by any of the antigens tested. On the other hand, addition of M phi or SRBC as additional "mitogens" along with LPS in the agar resulted in progeny colonies that could respond in vitro. Although M phi did not increase the number of colonies, their presence enhanced the size and in some cases the frequency of stimulatable colonies. These data complement earlier observations in suggesting that different B cell subpopulations may grow under different cloning conditions. Moreover, the ability to stimulate the clonal progeny of single B cells to antibody synthesis should permit further definition of triggering and tolerance events at the single-cell level.

Animals↗
PubMed1981

Hapten-specific murine colony-forming B cells. II. Delineation of a tolerogen-sensitive subpopulation of colony-forming B cells.

B cell subpopulations were studied by using B cell cloning procedures and an in vitro tolerance induction model. Fluorescein- (FL) specific B cells from normal spleens were isolated by using FL gelatin plates and were then cultured in semisolid agar in the presence or absence of tolerogen. Hapten-specific cells grew in soft agar to form discrete colonies. Colony growth is dependent on "mitogens" present in agar, sheep red blood cells (SRBC), and lipopolysaccharide (LPS). For example, SRBC plus LPS potentiate the growth of an increased number of colony-forming B cells (CFU-B) compared to either additive alone. These CFU-B could be triggered by a specific antigen to yield plaque-forming cells (PFC). With tolerogen (FL-sheep gamma-globulin) present in the agar, the number of FL-specific CFU-B was reduced by 25 to 50%. The ability of the remaining colonies to form PFC upon antigenic stimulation was also reduced. This reduction in CFU-B numbers, however, was observed only when the agar contained both SRBC and LPS as mitogenic potentiators of growth; no effect of tolerogen on CFU-B numbers was seen when cells were grown with either additive alone. Interestingly, the effect of tolerogen on CFU-B numbers was abrogated when peritoneal macrophages, in addition to SRBC plus LPS, were present during cloning. It is postulated that unique subpopulations of B cells form colonies under varied cloning conditions and that those CFU-B grown with SRBC plus LPS display an increased sensitivity to growth inhibition by tolerogen.

Animals↗
PubMed1981

The induction of tolerance and suppression in autoimmune MRL mice using hapten-modified self.

Disturbances in suppressor cell function have been considered important in the pathogenesis of systemic lupus erythematosus (SLE), a conclusion supported by studies with New Zealand mice. To determine whether other SLE mice display similar immunoregulatory defects, we investigated the susceptibility of autoimmune MRL mice to unresponsiveness induced by hapten-modified self (HMS). The response of splenocytes from MRL-lpr/lpr mice (lpr) was compared with those of sex- and age-matched, congenic MRL-+/+ mice (+/+), and H-2-identical (H-2k) CBA/J mice. Spleen cells (NSC) were cultured in vitro with hapten-modified syngeneic splenocytes (TNP-SC) and tested for responsiveness to TNP-LPS (for tolerance) or their ability to suppress the response of fresh cells. There was no difference in the susceptibility of lpr splenocytes from 3- and 10-mo-old mice to the induction of tolerance or suppression when compared with those from age-matched +/+ or CBA mice. To evaluate any quantitative defects in the responsiveness of lpr splenocytes to HMS, we modified the conditions under which suppressor activity was generated. Varying the ratio of NSC to TNP-SC from 10:1 to 2000:1, or changing the concentration of TNBS for haptenation from 10 mM to 0.5 mM per 10(8) spleen cells revealed no differences in the dose-response curves of lpr splenocytes for both tolerance and suppression when compared with those of the CBA. These results indicate that clinically affected MRL mice have intact suppressor cell activity in response to antigen-modified self and suggest a possible therapeutic role of this modality in inducing tolerance to self-antigens.

Aging↗
PubMed1980

Role of self carriers in the immune response and tolerance. V. Reversal of trinitrophenyl-modified self suppression of the B-cell response by blocking of H-2 antigens.

Trinitrophenylated syngeneic spleen cells (TNP-SC) are potent tolerogens of the anti-TNP plaque-forming cell (PFC) response in vivo and in vitro. This unresponsive state requires T cells for both its induction and maintenance. Because H-2K/D-restricted cytotoxic T cells are also induced by exposure to TNP-SC, we determined the role(s) of histocompatibility antigens (K, I, and D) in the suppression of the PFC response by TNP-SC. We treated syngeneic TNP-modified stimulator cells with antiserum directed at K-, I-, or D-region determinants and found that blocking of H-2K or D antigens on TNP-SC transformed these tolerogens into immunogens capable of eliciting an anti-TNP PFC response in the absence of extrinsic immunogens like TNP-polymerized flagellin. In H-2k or H-2a(k/d) mice, only H-2Kk needs to be blocked on the stimulator cells, whereas H-2K or D recognition was apparent in B10.A(4R) mice. These observations indicate that suppression of the PFC response by TNP-SC shows the same restriction in recognition as does the cytotoxic T-cell response. Furthermore, our results suggest that TNP-I-A is recognized by the helper cells in this system as the intrinsic antigen. When both TNP-K and TNP-I-A are present and available on the same stimulator cell, suppression (via modified K recognition) is dominant over help.

Animals↗
PubMed1980

Creation and properties of histocompatibility antigen-cell conjugates. I. Preparation and immunological properties of rat histocompatibility antigens.

A necessary step in the induction of unresponsiveness to transplantation antigens is the preparation and presentation of tissue antigens in a suitable form. A method is presented for obtaining rat histocompatibility antigen in a soluble, "heptenic" form suitable for coupling to a tolerogencie carrier. Lewis and ACI spleen cell membranes are solubilized with deoxycholate and purified by Lens culinaris affinity chromatography. The ultracentrifuged, solubilized preparation of rat histocompatibility (HC) antigen is unable to initiate immunity, but is able to react specifically with the product of an already established immune response. The HC antigen preparation is neither immunogenic nor tolerogenic alone. However, an antibody response to allogeneic cells can be prevented when these rat HC preparations are chemically coupled to tolerogenic carrier as described in the accompanying paper.

Animals↗