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E S Metcalf

Publications and source records attributed to E S Metcalf.

7 recordsLinked to original sources
PubMed1977

Expression of phosphorylcholine-specific B cells during murine development.

The TEPC 15 (T15) clonotype, a putatively germline antibody specificity, does not appear in the neonatal B-cell repertoire until approximately 1 wk of age. This report extends this observation by the demonstration that (a) the T15 clonotype follows similar kinetics of appearance in germfree as well as conventionally-reared mice; (b) maternal influences and genetic background play a minor role in the development of the T15 clonotype since CBFI neonates raised by C57BL/6 or BALB/c mothers acquire the T15 clonotype at the same time in ontogeny as BALB/c neonates; (c) the lack of phosphorylcholine (PC)-specific B cells shortly after birth is reflected in a dearth of PC-binding cells in the neonate as well; and (d) no PC-specifc B cells are found in 19-day fetal liver or in bone marrow until 7 days of life, coincident with their appearance in the spleen. These findings, along with a previous report that PC-specific splenic B cells are tolerizable as late as day 10 after birth, confirm the invariant, late occurrence of the T15 clonotype and support a highly- ordered, rigorously predetermined mechanism for the acquisition of the B- cell repertoire. The results are discussed in light of other studies on the ontogeny of B-cell specificity, and in terms of the implications on the mechanism by which antibody diversity is generated.

Animals↗
PubMed1977

In vitro tolerance induction of neonatal murine B cells as a probe for the study of B-cell diversification.

The susceptibility to in vitro tolerance induction has been implicated as a characteristic of B cells early in their development, since DNP-reactive B cells are tolerizable only during the first days after birth, and 25% of adult bone marrow cells are tolerizable. In the present study, a modification of the in vitro splenic focus technique was utilized to determine if PC-specific B cells, by virtue of their late expression (approximately 1 wk post-parturition), also display susceptibility to tolerance induction. The results demonstrate that at 7-10 days after birth, when over 90% of the DNP-specific splenic B cells are resistant to tolerance induction, the majority of PC-specific B cells are tolerizable. These results re-emphasize tolerance susceptibility as a characteristic of developing clones, confirm the late acquisition of PC-specific B cells, and support the contention that the acquisition of the specificity repertoire is a highly ordered, specifically predetermined process which is independent of antigen-driven events.

Animals↗
PubMed1976

In vitro tolerance induction of neonatal murine B cells.

The susceptibility of neonatal and adult B lymphocytes to tolerance induction was analyzed by a modification of the in vitro splenic focus technique. This technique permits stimulation of individual hapten-specific clonal precursor cells from both neonatal and adult donors. Neonatal or adult BALB/c spleen cells were adoptively transferred into irradiated, syngeneic, adult recipients which had been carrier-primed to hemocyanin (Hy), thus maximizing stimulation to the hapten 2,4-dinitrophenyl coupled by Hy (DNP-Hy). Cultures were initially treated with DNP on several heterologous (non-Hy) carriers and subsequently stimulated with DNP-Hy. Whereas the responsiveness of adult B cells was not diminished by pretreatment with any DNP conjugate, the majority of the neonatal B-cell response was abolished by in vitro culture with all of the DNP-protein conjugates. During the 1st wk of life, the ability to tolerize neonatal splenic B cells progressively decreased. Thus, tolerance in this system is: (a) restricted to B cells early in development; (b) established by both tolerogens and immunogens; (c) achieved at low (10(-9) M determinant) antigen concentrations; and (d) highly specific, discriminating between DNP- and TNP-specific B cells. We conclude that: (a) B lymphocytes, during their development, mature through a stage in which they are extremely susceptible to tolerogenesis; (b) the specific interaction of B-cell antigen receptors with multivalent antigens, while irrelevant to mature B cells, is tolerogenic to neonatal (immature) B cells unless antigen is concomitantly recognized by primed T cells; and (c) differences in the susceptibility of immature and mature B lymphocytes to tolerance induction suggest intrinsic differences between neonatal and adult B cells and may provide a physiologically relevant model for the study of tolerance to self-antigens.

Age Factors↗
PubMedDate not supplied

Assessing B cell diversification by antigen receptor and precursor cell analysis.

A major element in the understanding of B cell specificity diversification is the extent of diversity present in mature and in developing B cell populations. Two general methods are currently used for assessing the specificity repertoire: (a) the enumeration of cells whose receptors can bind a specific antigen, and (b) the enumeration of cells which can respond to antigenic stimulation by antibody-forming cell clone production. Our laboratory has utilized the latter method to establish the frequency of B cells responsive to a wide variety of antigenic determinants. The findings indicate that: (a) the primary murine B cell specificity repertoire probably includes more than 10(7) clonotypes; (b) some clonotypes are represented by numerous B cells (40,000 TEPC 15 precursors per BALB/c mouse) while most are represented by fewer than to B cells per mouse; (c) the acquisition of the repertoire is apparently antigen-independent since germfree mice have repertoires similar to conventional mice and secondary B cells are easily distinguished from primary B cells; (d) the neonatal repertoire appears to contain only 10(4) clonotypes at birth, each represented by perhaps 200-400 cells; (e) the diversification process from neonatal to adult repertorie appears highly ordered and reproducible. Antigen binding cell studies have now used in conjunction with the splenic focus assay in an attempt to correlate these two techniques. The results indicate that the efficiency of the splenic focus assay used for precursor cell anlysis it 4-5% for both primary and secondary B cells and is similar to the percent of donor B cells lodged in recipient spleens. For certain antigens (DNP-BSA) the number of antigen-binding cells can represent 4% of the total B cells, and this number directly correlates with the concentration of antigen used; stimulation, on the other hand, appears to have an affinity threshold achieved by only 0,02% of the DNP-specific B cells. In contrast, PC-BSA antigen-binding cell and splenic focus precursor cell frequencies are identical. These findings are interpreted to indicate that antigen-binding cell analyses confirm the validity of the calculations used to estimate precursor frequencies in the splenic focus technique. However, for some antigens binding to cell receptors, one detects a large number of cells belonging either to a nonstimulatable B cell subclass or whose receptor affinity is too low to permit stimulation.

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