The Fcγ Receptor IIA-R/R131 Genotype Is Associated with Severe Sepsis in Community-Acquired Pneumonia

Community-acquired pneumonia (CAP) can be caused by a variety of microorganisms but is most frequently associated with Streptococcus pneumoniae and gram-negative bacteria like Haemophilus influenzae. Encapsulated bacteria are able to escape phagocytosis, unless they are bound by immunoglobulin G2 subclass antibodies. These antibodies interact with Fc gamma receptor IIa (Fc gamma-RIIa), thereby facilitating opsonophagocytosis of the encapsulated bacteria. We studied the relationship between the Fc gamma-RIIa-R/H131 polymorphism and the clinical course of CAP and pathogen-specific susceptibility. Regarding methodology, the Fc gamma-RIIa genotype R/H131 was determined in 200 patients with CAP and in 313 healthy controls and was correlated with the clinical course, laboratory parameters, and causative microorganism. The Fc gamma-RIIa-R/R131 genotype was found more frequently in patients with severe sepsis (odds ratio [OR], 2.55; 95% confidence interval [CI], 1.30 to 5.00; P < 0.01). The majority of patients in this group suffered from invasive pneumococcal disease. The duration of hospital stay was longer for patients with the Fc gamma-RIIa-R/R131 genotype. Fc gamma-RIIa genotypes were not associated with an increased risk of CAP in general; however, the Fc gamma-RIIa-R/R131 genotype was found more frequently in patients with CAP caused by H. influenzae than in controls (OR, 3.03; CI, 1.04 to 9.09; P < 0.05). In conclusion, the Fc gamma-RIIa-R/R131 genotype is associated with severity of CAP and is more frequent in CAP caused by H. influenzae.