Human immune response to group A streptococcal carbohydrate (A-CHO). I. Quantitative and qualitative analysis of the A-CHO-specific B cell population responding in vitro to polyclonal and specific activation.

Abstract

The immune response to the group-specific carbohydrate of group A streptococci (A-CHO) provides an informative in vitro model for the investigation of several aspects of human anticarbohydrate immune responses. A-CHO-specific B cells can be polyclonally activated by pokeweed mitogen (PWM), and, specifically, by in vitro immunization with streptococcal vaccine. High levels of A-CHO-specific antibodies, mainly directed to the immunodominant side chain N-acetyl-D-glucosamine (GlcNAc), occur in healthy adult individuals. Serum antibody levels are reflected in high frequencies of precursor B cells among peripheral blood lymphocytes. In one particular case, greater than 15% of all B cells activated by PWM for IgM production were found to produce IgM anti-A-CHO antibodies, as determined in limiting dilution experiments, as well as by analyzing Ig concentrations in bulk culture experiments. The case with the lowest proportion observed had 0.3% A-CHO-specific B cells among IgM-producing B cells. Preferential PWM activation of anti-A-CHO-producing B cells could be excluded. The comparison of the proportions of anti-A-CHO IgM produced in vivo, and of B cells producing antibodies of this specificity in peripheral blood, suggests a similar distribution of specific precursor B cells in the antibody-producing lymphoid tissue compartments and in peripheral blood. However, nearly all specific antibodies produced in vitro belong to the IgM isotype, whereas IgG anti-A-CHO in high amounts, mostly exceeding the specific IgM, was found only among anti-A-CHO antibodies produced in vivo. Low anti-A-CHO IgG production was seen in polyclonally activated as well as in antigen-activated cultures, whereas, in contrast, total IgG was produced in considerable amounts after polyclonal activation. This suggests a different distribution pattern, and/or diverse differentiation requirements for anti-A-CHO-producing B cells, compared with other B cell species.

Manipulation of the glycan‐specific natural antibody repertoire for immunotherapy

“…GlcNAc is the constituent monosaccharide of chitin (the second most abundant biopolymer on earth) which is a structural component of many microorganisms, and GlcNAc residues are present in cell wall antigens of many common pathogens, including Group A Streptococcus (GAS) . In mammals, GlcNAc residues exist in several forms resulting from post‐translational modification; however, it is most commonly found as a cryptic epitope buried within the context of mature glycan chains .…”

“…GlcNAc‐specific antibodies are common in the human population . Therefore, using open‐source microarray data from the Consortium for Functional Glycomics (data generated by Dr. Nicolai Bovin, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russian Federation), we analyzed the conservation of antibody reactivity with truncated glycan products in healthy human serum.…”

“…Early studies in mice suggest that GlcNAc‐specific antibody clonotypes are highly restricted in their IGHV gene usage, giving rise to a pauciclonal antibody repertoire . GlcNAc‐specific antibodies in humans are also restricted, and idiotypes of GlcNAc‐specific Abs appear to be highly conserved in the human population . Interestingly, certain GlcNAc‐reactive Ab‐associated idiotypes in humans demonstrate antibody isotype‐restriction , which may be indicative of differing roles of variable fine‐specificities within the GlcNAc‐specific B cell compartment.…”

Human immune response to group A streptococcal carbohydrate (A‐CHO) III. Comparison of the efficiencies of anti‐idiotopic antibody and of nominal antigen in the induction of IgM anti‐A‐CHO‐producing B cells

“…As has been reported earlier Strep. A were able to induce an IgM anti-A-CHO response in blood B cells [5]. In this study peripheral B cells from three normal donors were subjected to in vitro stimulation with either solid-phase anti-Id498 antibody or bacterial antigen.…”

“…Antigen preparations (A-CHO and treatment of the Strep. A bacteria) were obtained as described before [5]. B cells were co-cultured with either irradiated or unirradiated T cells in a 1 : 2 ratio; the absolute number of B cells remained constant.…”