Complement activation by polyclonal immunoglobulin G1 and G2 antibodies against Staphylococcus aureus, Haemophilus influenzae type b, and tetanus toxoid

Abstract

To obtain information on effector functions of human immunoglobulin G2 (IgG2), we have measured the complement-activating properties of polyclonal IgG subclass antibodies against bacterial antigens. IgGl and IgG2 were purified from serum samples from five healthy individuals, and complement activation was measured with different bacterial antigens. We used Staphylococcus aureus Wood 46 (STAW), which is a common antigen, Haemophilus influenzae type b (Hib), which is a common pathogenic microorganism in children, and formaldehyde-inactivated tetanus toxin (IT). Bacteria were incubated with antibodies and then incubated with sera from agammaglobulinemic patients as a complement source, and C3c deposition was measured by enzyme-linked immunosorbent assay. We found that anti-STAW IgG2 activated complement to a level similar to that of anti-STAW IgGl. Anti-Hib IgGl complement activation was as much as seven times higher than that of anti-Hib IgG2 in four individuals. In one individual, anti-Hib IgG2 was more effective in complement activation than anti-Hib IgGl. Anti-TT antibodies showed patterns similar to those of anti-Hib. Our results indicate that IgG2 antibodies may contribute significantly to antibacterial defense. Also, individual differences in antibody effector functions should be taken into account when evaluating the immune status of patients and during early phase 1 studies of new vaccines.

Opsonophagocytic and Bactericidal Activity Mediated by Purified IgG Subclass Antibodies After Vaccination with the Norwegian Group B Meningococcal Vaccine

“…The purity of each subclass after separation ranged from 100% to 86% (Table 1), which is in the same range as found previously using similar separation methods [13]. While IgG3 was separated without denaturing conditions, IgG2 and IgG1 were eluted from Protein A at pH 4.6 and 4.0, respectively.…”

“…Lortan et al [9] showed a significant correlation between phagocytosis and the serum level of anti-pneumococcal polysaccharide antibodies of the IgG1 and, in particular, the IgG2 subclass, although they did not test each subclass as purified preparations. Bredius et al studied opsonophagocytic activity [10] and complement activation [13] of purified IgG1 and IgG2 antibodies against Staphylococcus aureus and Haemophilus influenzae type b. They proved IgG2 in several instances to be just as effective as IgG1.…”

“…Pure IgG3 was eluted with this buffer, while all other plasma proteins were retained on the column. IgG2 antibodies were separated from IgG1 using pH gradient elution from Protein A [13]. The IgG2-rich fraction was eluted between pH 5.2 and pH 4.6, whereas the corresponding IgG1rich fraction was eluted between pH 4.6 and pH 4.0.…”

“…However, this may not be representative for polyclonal IgG antibodies, differing in specificities and affinities, induced by infection or vaccination. There have been some studies on the functional activity of the IgG1 and IgG2 subclasses from clinical materials, both concerning phagocytosis [9][10][11] and bactericidal activity [12,13]. These antibodies were mainly directed against polysaccharide and may thus not be representative for antibodies against protein antigens that may have a rather differing distribution on the microbial surface.…”

Immunoglobulin G2 antibodies promote neutrophil killing of Actinobacillus actinomycetemcomitans

“…However, neither of these situations is entirely physiologic. On the other hand, more recent studies with polyclonal IgG2 antibodies directed to diverse bacterial antigens indicate that these antibodies exhibit significant anticomplementary activity, as measured by fixation of C3c (6). In addition, complement has been reported to enhance phagocytosis of IgG2-coated bacteria by neutrophils (2,5).…”