Phagocytosis of bacteria constitutes an important defense mechanism against invasive bacterial diseases. Efficacy of phagocytosis by polymorphonuclear neutrophils is known to vary between allotypes of Fc gamma RIIa (a class of Fc receptors for immunoglobulins that is constitutively expressed on neutrophils). We compared the distribution of Fc gamma RIIa-R131 and Fc gamma RIIa-H131 allotypes in 98 Slavic complement-sufficient patients with meningococcal disease with that of the allotypes in 107 healthy controls. A strong association was found between the IIa-R/R131 allotype and the development of meningococcal disease after the age of 5 years, compared with IIa-R/H131 and IIa-H/H131 allotypes (P < .03; odds ratio [OR], 2.9). A severe course of meningococcal disease was observed in 21 (68%) of 31 episodes in patients with IIa-R/R131 genotype and in 22 (54%) of 41 episodes in patients with IIa-R/H131 genotype, in contrast to eight (31%) of 26 episodes in patients with IIa-H/H131 genotype (P < .02; OR, 4.7). Our data show that individuals older than 5 years of age who have the IIa-H/H131 allotype are less susceptible to severe meningococcal disease than are individuals with the IIa-R/R131 or IIa-R/H131 genotype.

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Late complement component‐deficient (LCCD) individuals lack plasma bactericidal activity and are highly susceptible to meningococcal disease. Phagocytosis plays a significant role in immune defence against meningococci and involves FcγRIIa (CD32) on leucocytes. Two allotypic forms are currently recognized: FcγRIIa‐R131 and RIIa‐H131. Neutrophils with the IIa‐H/H131 allotype are more effective in phagocytosis than IIa‐R/R131. We studied the distributions of IIa‐R131 and IIa‐H131 allotypes among 29 Russian LCCD patients who had suffered from recurrent episodes of meningococcal disease. The distribution of IIa‐R/R131 to heterozygous IIa‐R/H131 to homozygous IIa‐H/H131 genotypes was 0.14:0.29:0.57 for LCCD patients who developed the first episode of disease before 10 years of age. The distribution was 0.21:0.64:0.14 for patients who experienced meningococcal disease above the age of 10 years (χ2 = 6, P < 0.05, odds ratio for IIa H/H131 versus R/R131 = 8). Meningococcal disease had a ‘grave’ course in 14 of 31 disease episodes in patients with IIa‐R/R131 and IIa‐R/H131 allotypes, in contrast to 1 of 18 episodes in patients with IIa‐H/H131 allotype (χ2 = 7, P < 0.01, odds ratio = 14). We conclude that IIa‐H/H131 individuals appear to have a higher acquired antibody‐mediated phagocytosis‐dependent resistance to meningococcal disease above the age of 10 years. Additionally, effective CD32‐mediated phagocytosis may restrict the severity of meningococcal disease in LCCD patients with IIa‐H/H131 phenotype.

Background: Thirty-one Russian patients with late complement component deficiency (LCCD) who had experienced one to five meningococcal infections were immunized with meningococcal polysaccharide vaccine (A + C + W135 + Y) and were followed for 3–8 years. We investigated the potentially protective killing effect of human neutrophils (PMNL) on serogroup A and W135 meningococci. Methods: Meningococci were incubated in LCCD vaccinee sera in the absence or presence of PMNL, and the number of live bacteria (CFU) was determined by plating onto chocolate agar. Results: When meningococci were incubated in the LCCD sera alone, exponential growth of meningococci occurred despite the presence of meningococcal antibodies. After the addition of PMNL, meningococci were inhibited in their growth or even eliminated. Group A or W135 meningococci were killed effectively by PMNL in 80% of the sera which were collected 1 month to 1 year after vaccination compared to only 40% in the prevaccination LCCD sera (p < 0.05). Three years after vaccination 67% of the LCCD sera were still capable of promoting killing (and even 90% after revaccination). The rate of killing correlated with the concentration of serogroup-specific immunoglobulins. In 83% of the 72 LCCD sera with more than 5 µg/ml anti-group A immunoglobulins the killing of group A meningococci was promoted. By contrast, only 21% of 19 samples with lower specific antibody levels showed a PMNL-mediated meningococcal killing (p < 0.05). The same effect was observed for group W135 meningococci. Conclusion: PMNL kill meningococci during incubation in LCCD serum; this effect increases after vaccination and depends on both specific antibody and complement. Protection by vaccination may therefore be caused by an increased killing capacity of PMNL.