Production of predominantly polymeric IgA by human peripheral blood lymphocytes stimulated in vitro with mitogens.

Abstract

Human peripheral blood lymphocytes (PBL) were cultured for various time periods (up to 8 d) in the presence of pokeweed mitogen (PWM), lipopolysaccharide, or Epstein-Barr virus. Cell-free supernates were fractionated on a standardized ultrogel AcA 22 column and the proportion of polymeric and monomeric IgA was determined by radioimmunoassay. The results demonstrate that PBL stimulated with these mitogens produce IgM and IgG with molecular characteristics identical to those found in serum, but that the IgA produced is predominantly of the polymeric type. To prove that this IgA represented disulfide bond-linked polymers rather than aggregated monomers, we have demonstrated that the high molecular weight IgA (a) maintains its polymeric form upon treatment with acidic buffers, (b) contains J chain, a glycoprotein associated only with polymeric immunoglobulins, and (c) dissociates to the monomeric form upon reduction of disulfide bonds. After 1 wk in culture, approximately 60% of the PWM-stimulated cells that contained IgA were positive for IgA2, whereas 40% were IgA1 positive as determined by immunofluorescence. Therefore, peripheral blood contains a population of lymphocytes with the potential to display, after appropriate stimulation and differentiation, characteristics similar to IgA cells found in external secretory tissues. The demonstration of the presence of such cells in the peripheral circulation suggests that these cells are precursors of IgA-producing plasma cells with the potential to populate mucosal tissues.

In vitro regulation of IgA subclass synthesis. I. Discordance between plasma cell production and antibody secretion.

“…Previous experiments demonstrated a predominance of IgA~ plasma cells early in the P W M response, at days 3 and 4; however, by day 7 of culture, the proportion of IgA2 plasma cells was equal to that of IgA1 (5). This suggested that the maturation of IgA2 plasma cells might be delayed compared with that of IgA1, and that if the culture period were extended, higher concentrations of IgAz might be found in culture supernatants.…”

IgA antibody-producing cells in peripheral blood after antigen ingestion: evidence for a common mucosal immune system in humans.

“…In contrast, IgA and IgM antibodies to both RR extract and Ag I/II increased by days [21][22][23][24] in both parotid saliva and tears from all subjects studied but one (donor 3). Individual values are presented as in Table 1.…”

Steady-state generation of mucosal IgA+ plasmablasts is not abrogated by B-cell depletion therapy with rituximab

“…2 Indicative of their generation in mucosal immune responses and very similar to plasmablasts circulating during steady state, 1 more than one-half of plasmablasts/ plasma cells detectable before and throughout B-cell depletion therapy expressed IgA, and the same cells predominantly coexpressed CCR10 and to a lesser extent ␣ 4 ␤ 7 integrin. 23,24 The IgA secreted by these plasmablasts in patients with RA showed rheumatoid factor reactivity only in single patients, whereas secretion of antimicrobial antibodies was detected in all patients as well as controls. In this regard, commensal microbes specifically induce secretory IgA production in the intestine of normal mice.…”