Akira Shida

Genetic Aspects of Serum Immunoglobulins and Respiratory Chemosensitivity

The role of genetics and environmental factors determining serum concentrations of immunoglobulins (IgA, IgG, and IgM,) were analyzed in 20 pairs of monozygotic (MZ) and 11 pairs of dizygotic (DZ) twins. Respiratory chemosensitivity to hypoxia and hypercapnia was also measured. Intrapair variances for alpha 2-, beta-, and gamma-globulins, IgG, IgA, and IgM were significantly smaller than interpair variances in MZ, indicating that these variables are more similar between pairs than among pairs in MZ. In DZ, intrapair variance for IgM was significantly smaller than interpair variance. Intrapair variance in MZ for gamma-globulin, IgG, IgA, hypoxic ventilatory response, and hypercapnic ventilatory response were significantly smaller than those in DZ, indicating that these variables are genetically controlled. Subjects with low IgA showed a blunted hypoxic ventilatory response, and subjects with high IgA, a vigorous ventilatory response. These results indicate that while IgM is controlled predominantly by environmental factors, IgA and IgG are genetically determined in young healthy subjects. Serum IgA levels and hypoxic ventilatory response are interrelated in young healthy subjects.

Genetic and Environmental Influence on Inspiratory Resistive Load Detection

To differentiate genetic factors from environmental forces in determining threshold for resistance load detection (RLD), 62 healthy adolescent twins (mean age = 16 years) and 74 healthy adult twins (mean age = 34 years) were studied by the standard psychophysical technique. The zygosity was determined by blood groups, finger prints, and physical appearances. Mean values for age, height, weight, pulmonary functions (FVC, FEV1, FEV1/FVC, Raw, and FRC) were not different between monozygotic (MZ) and dizygotic (DZ) pairs either in adolescent or adult twins. Threshold for RLD was analyzed in terms of added resistance divided by airway resistance plus apparatus resistance (Weber fraction) and mouth pressure (P) at the threshold. Both Weber fraction and P were equivalent between MZ and DZ either in adolescent or adult twins. In adolescence, within-pair variance for P was significantly greater in DZ than in MZ, but within-pair variances for Weber fraction were similar between MZ and DZ, the former indicating that threshold for RLD is predominantly influenced by genetic factors. In adults, within-pair variances for Weber fraction and P were not different between MZ and DZ, indicating that environmental factors predominate over genetic factors. When adolescent and adult twins were lumped together, mean values for Weber fraction and P were not different between male and female. Relationship between P and age was significant both in male and female. P (male) = 0.281 + 0.013 X age (years) +/- SD 0.36 cm H2O, and P (female) = 0.235 + 0.013 X age (years) +/- 0.48 cm H2O. These results indicate that the threshold for RLD is influenced predominantly by genetic factors in adolescence, but environmental factors predominate in the adult. Although sex difference is not clear, P at the threshold increases with age in both sexes.