title: Causal analysis of the variability of IgA, IgG, and IgM immunoglobulin levels.
abstract: The interindividual variability of IgA, IgG, and IgM immunoglobulin levels was studied using path analysis in a northeastern Brazilian sample (nuclear families) to determine the genetic and/or environmental causes of their variation. The path analysis model decomposes the phenotype into genetic causes (autosomal and X-chromosome-linked genes) and environmental causes. A significant familial aggregation, mainly resulting from autosomal components, was detected for the 3 immunoglobulin levels. The values of genetic heritability were h2 = 0.410 +/- 0.030 for IgA, h2 = 0.617 +/- 0.020 for IgG, and h2 = 0.540 +/- 0.023 for IgM, and the values for environmental-cultural heritability were c2 = 0.085 +/- 0.034 for IgA, c2 = 0.084 +/- 0.027 for IgG, and c2 = 0.023 + 0.023 for IgM. Our results did not show a heritable component resulting from X-chromosome-linked genes on IgM levels, as suggested by some studies (Wood et al. 1969; Grundbacher 1972; Purtilo and Sullivan 1979). Some additional results were that (1) age and IgA concentration were positively correlated, with IgA level increasing gradually from childhood to adulthood (p < 0.001); (2) sex and the age X sex interaction act on IgG concentration (p < 0.01); (3) age and IgM concentration are correlated (with children presenting lower levels than adults, especially in males, p < 0.01); and (4) a significant association exists between sex and IgM level (with females presenting higher levels than males, p < 0.001).
authors.affiliation: Departamento de Genética, Instituto Oswaldo Cruz, Rio de Janeiro, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Hatagima
authors.forename: P H
authors.initials: PH
authors.lastname: Cabello
authors.forename: H
authors.initials: H
authors.lastname: Krieger
mesh_terms: D000328:Adult; D000367:Age Factors; D001938:Brazil; D002648:Child; D004777:Environment; D005260:Female; D008040:Genetic Linkage / Q000235:genetics; D014644:Genetic Variation / Q000235:genetics*; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood* / Q000235:genetics*; D007074:Immunoglobulin G / Q000097:blood* / Q000235:genetics*; D007075:Immunoglobulin M / Q000097:blood* / Q000235:genetics*; D008297:Male; D008957:Models, Genetic; D012737:Sex Factors; D014960:X Chromosome / Q000235:genetics
chemical_list: D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M