The expression of a set of antibody variable regions in lipopolysaccharide‐reactive B cells at various stages of ontogeny and its control by anti‐idiotypic antibody

Abstract

An analysis is presented in which we measure the expression of a subset of antibody variable (V) regions in lipopolysaccharide (LPS)-reactive precursor B cells at various stages of ontogeny. The V regions were characterized by hapten (4-hydroxy-3-nitrophenyl)acetyl (NP)-binding specifity and/or expression of idiotypic determinants whose genetic basis had been explored in previous studies. Only V regions containing the V lambda 1 domain were considered: this allowed an unequivocal determination of idiotopes and reduced heterogeneity in the system essentially to the multiplicity of VH and D genes. It was found that approximately every fourth lambda 1-bearing LPS-reactive splenic B cell produces an NP-binding antibody. Approximately 1 in 40 lambda 1-bearing cells expressed an idiotope (Ac38) which is encoded by V lambda 1 and a set of related VH genes in combination with D and J elements. Of these cells, only a minority produce an NP-binding antibody and a few percent of the latter express a second idiotope (Ac146) which is known to be restricted to a subset of Ac38-positive, NP-binding humoral antibodies. All these frequencies are in good accord with previous analyses of anti-idiotope-induced antibodies in the serum. They can be easily accommodated into a simple model of random selection of VH genes in LPS-reactive B lymphocytes. The frequencies of the V regions under study were essentially the same in LPS-reactive B cells from spleens of adult and newborn animals and in LPS-reactive B cells generated from bone marrow pre-B cells in vitro. In the case of the latter cells the frequencies were independent of the absence or presence of T cells in the culture system. While we could thus detect, in naive mice, neither positive nor negative selection of the cells from the time of their generation in the bone marrow until their arrival in the periphery, negative selection is in principle possible: the presence of microgram amounts of anti-idiotope antibodies during maturation from pre-B to B cells specifically blocks the appearance of idiotope-bearing LPS-reactive cells in vitro. The potential physiological role of the latter effect in the sense of self-stabilization of the expressed antibody repertoire in ongoing immune responses and the possibility that frequency determinations in LPS-reactive B cells may be not representative for the repertoire expressed in the population of mature B cells is discussed.

Membrane IgE Binds and Activates FcεRI in an Antigen-Independent Manner

“…The sensitivity of the assay was 5 ng/ml. The mouse anti-human Fc⑀RI␣ mAb 9E1 and the mouse anti-SV5 mAb have already been described (16,20,21), and the mouse anti-(anti-NIP) Id mAb AC38 (22) was kindly provided by S. Burastero (San Raffaele Scientific Institute, Milan, Italy).…”

A Critical Role for B Cells in the Development of Memory CD4 Cells

“…We took advantage of the well-characterized response of IgH b mice to the nitrophenyl (NP) hapten in the B cell population bearing the light chain of Ig (39). Enrichment of ϩ B cells from these mice results in the presence of a high FACS sorted frequency of normal, naive B cells that bind NP (40). We transferred -bearing B cells into MT mice immunized with NP-KLH and determined the frequency of memory CD4 cells 30 days later.…”

“…We chose this model since it approximates a physiological situation where we envision that initial priming of naive CD4 cells occurs via DC (25) and activated B cells assume a greater role in cell-cell interactions as the response progresses. ϩ B cells were used as a source of Ag-presenting B cells since a high frequency of these cells bind to the hapten NP (39,40). These B cells were pulsed by overnight culture with NP-KLH in the presence of rIL-4.…”

Role of variable region gene expression and environmental selection in determining the antiphosphorylcholine B cell repertoire.

“…Additionally, clonotype distributions (such as the expression of high frequency predominant specificities) that characterize the mature primary B cell repertoire also characterize the prereceptor B cell repertoire. Thus, neither antigenic stimulation nor idiotypic selection are required for repertoire diversification (15) or predominant clonotype expression (16,33,34). It also appears that clonal expansion precedes sIg expression, so that expressed specificities are represented by clones of multiple pre-B cells and B cells.…”