Agnès Langendries

Lack of SC/pIgR-mediated epithelial transport of a human polymeric IgA devoid of J chain: in vitro and in vivo studies.

Three human polymeric IgA (pIgA) myeloma proteins of tetrameric size were compared for their J‐chain content, their in vitro secretory component (SC)‐binding ability, and their capacity to be transcytosed by polymeric immunoglobulin receptor (pIgR)‐expressing epithelial cells in vitro and rat hepatocytes in vivo. One of the three pIgA preparations, pIgA‐L, was shown to lack J chain and was unable to combine with purified free human and rat SC, whereas pIgA‐G and pIgA‐C contained J chain and combined readily with SC. Furthermore, pIgA‐L was not transferred into rat bile after intravenous injection, and was hardly transported apically by polarized Madin–Darbey canine kidney cell monolayers expressing the human pIgR, whereas pIgA‐G and pIgA‐C were efficiently transported in both test systems. Together with our recent demonstration that antibodies to human J chain block the SC/pIgR‐mediated epithelial transport of pIgA, these data unanimously confirm the proposed key role of J chain in the epithelial transport of polymeric immunoglobulins into exocrine secretions.

Homogenous IgA monomers, dimers, trimers and tetramers from the same IgA myeloma serum.

Starting from two IgA1 myeloma sera, the isolation of monoclonal monomeric, dimeric, trimeric and tetrameric IgA in a high state of purity and size homogeneity for each serum is described. The method combined repetitive gel filtrations on Ultrogel AcA22 with affinity chromatography on Jacalin-Sepharose. These various forms of pure polymeric IgA obtained from the same monoclonal IgA should allow a precise comparison of their respective structure and reactivity with different IgA-binding proteins, such as IgA Fc-receptors, the polymeric Ig receptor, and lectins.

Secretory component production by human bronchial epithelial cells is upregulated by interferon gamma.

Secretory immunoglobulin A (S-IgA) participates in the first noninflammatory line of defence of the respiratory tract. S-IgA consists of dimeric IgA (dIgA) produced by plasma cells and secretory component (SC) produced by epithelial cells. This study compared SC production by primary cultures of human bronchial epithelial cells (HBEC) and by respiratory epithelial cell lines. Among the cell lines, A549 did not produce detectable SC, 16HBE produced very low levels of SC, while CALU-3 produced significant levels of SC. HBEC produced SC in nonpolarized and polarized primary cultures, where it was secreted apically. Polarized HBEC transcytosed radiolabelled and cold dIgA, resulting in the presence of S-IgA in their apical media. SC production and IgA transcytosis by polarized HBEC were upregulated by interferon-gamma (IFN-gamma) after 48 h. By reverse transcription-polymerase chain reaction, no SC messenger ribonucleic acid (mRNA) was detected in A549 and 16HBE, while SC mRNA in CALU-3 was comparable to that of HBEC incubated for 48 h with IFN-gamma. By immunocytochemistry, HBEC expressed SC immunostaining and its intensity increased after 48 h with IFN-gamma. It is concluded that human bronchial epithelial cells produce secretory component and transcytose dimeric immunoglobulin A in vitro. These processes were apically polarized and upregulated by interferon-gamma. Among the cell lines studied, only CALU-3 expressed secretory component-messenger ribonucleic acid and produced detectable secretory component.

Contribution of serum IgA to intestinal lymph IgA, and vice versa, in minipigs.

Immune cells in pig gut lymph are rather well studied, but data on gut lymph immunoglobulins and their origin are nonexistent. Such data are important to understand the interplay between pig systemic and intestinal immunity as a basis for vaccination studies. In some species, gut lymph contributes much to plasma IgA, but apparently not in humans. To estimate the contributions of pig serum IgA to intestinal lymph IgA and vice versa, concentrations of IgA, IgG, IgM, albumin, haptoglobin, C3 and alpha 2-macroglobulin were measured by radial immunodiffusion in paired porcine intestinal lymph and serum samples. All proteins, except IgA, had lymph/serum ratios (< 1.0) inversely related to their size, depending on passive diffusion from serum. The mean lymph/serum ratio of IgA was 2.2 instead of an expected 0.50 or 0.65 (dimer or monomer, respectively), indicating that of the IgA in gut lymph, 22.7 or 29.5% came from serum, vs 77.3 or 70.5% from the intestine. Percentage of polymeric IgA, measured by gelfiltration and corrected radial immunodiffusion, was 64.3% in porcine mesenteric lymph and 47.3% in serum. As the pig plasma volume and daily gut lymph flow into circulation were known, it could be calculated that roughly 31% of the total plasma IgA originated daily from local intestinal synthesis, reaching blood via mesenteric lymph.

Cholera toxin neutralization: a comparison of purified serum IgG and biliary secretory IgA antibodies.

Rats were immunized three times with cholera toxin via the intraintestinal or intravenous route, and their respective biliary secretory IgA (sIgA) or serum IgG antibodies were affinity-purified on a cholera toxin immunoabsorbent. On a molar basis, the sIgA antibodies were roughly seven-fold more efficient than IgG antibodies in neutralizing cholera toxin in the ligated intestinal loop assay. Various explanations for this difference in neutralizing capacity are proposed.

Mouse Secretory Component

The receptor for polymeric immunoglobulins (plg-R) has already been extensively studied in many species, but not much in mice1, the most common laboratory animals. This study was conducted to isolate and characterize mouse secretory component (SC) and/or plg-R and to produce an antiserum allowing immunolocalization of mouse SC/pIg-R as well as the study of its expression modulated by various cytokines.

Peptic fragments of rat monomeric IgA.

The structure of rat IgA is still poorly known, despite the existence of rat monoclonal IgA myeloma and hybridoma proteins. This paper describes the peptic digestion fragments of two monomeric myeloma and two monomeric hybridoma (anti-dinitrophenyl [DNP]) rat IgA proteins. In the case of one hybridoma (LO-DNP-67), but not in the three other cases, the peptic digest comprised, besides the expected F(ab’)α-like fragments, also an Fcα-like fragment.