RESUMEN
Oral contraceptive (OC) use has been associated with increased incidence of a number of infections, but the mechanisms behind these changes is unclear. The present study compared OC users and nonusers in natural killer (NK) cell activity, NK phenotype, and illness frequency. Subjects were 55 female medical students (19 OC users, 36 nonusers). Three blood samples were obtained, 1 mo apart. Natural cytotoxicity was tested with a 51Cr assay. Self reports of illness symptoms during the previous week were collected at each blood sampling. NK phenotype number was assessed by flow cytometry. Oral contraceptive users had lower natural cytotoxicity and increased frequency of sneezing, gastrointestinal distress, runny nose, sore throat, coughing, and total illness symptoms, relative to nonusers. No differences were found between OC users and nonusers in NK phenotype number. These findings support the hypothesis that differences between users and nonusers in infection rates might be due to alterations in NK activity.
PIP: Oral contraceptive (OC) use has been associated with increased incidence of a number of infections, but the mechanisms behind such changes are unclear. Comparison of lymphocyte phenotypes between contraceptive users and nonusers found no difference in either the percentage or absolute numbers of any cell types. Other data, however, suggest differences in natural cytotoxic activity in contraceptive users. Natural cytotoxic activity in normal women has been found to vary with menstrual phase and estradiol levels, being lowest mid-cycle, shortly following peak estradiol levels. OC users, however, demonstrate no variation in either natural killer (NK) cell activity or estradiol levels over their cycles. The authors report their findings from a study comparing 19 OC users and 36 nonusers in NK cell activity, NK phenotype, and illness frequency. Three blood samples were obtained one month apart from each of the female medical student participants. Natural cytotoxicity was tested with a Cr assay, while NK phenotype number was assessed by flow cytometry. Relative to nonusers, OC users had lower natural cytotoxicity and increased frequency of sneezing, gastrointestinal distress, runny nose, sore throat, coughing, and total illness symptoms. No differences were found between OC users and nonusers in NK phenotype number. These findings support the hypothesis that differences between users and nonusers in infection rates may be due to alterations in NK activity.
