Sex- and age-dependency of IgG auto-antibodies against IL-1 alpha in healthy humans.
Naturally occurring anti-interleukin (IL)-1 alpha IgG antibodies (Ab-IL-1 alpha) were measured in sera of 466 healthy Danish blood donors. Ab-IL-1 alpha bound IL-1 alpha with exceptionally high affinity (Kd: 10(-11) M) and neutralized both cell-associated and extracellular IL-1 alpha but not IL-1 beta or IL-1 receptor antagonist. More than 80% of the saturable binding of rIL-1 alpha to serum was to Ab-IL-1 alpha, suggesting that these antibodies are the quantitatively most important IL-1 alpha-binding components in serum. Judged by second antibody precipitation assay, the prevalence of Ab-IL-1 alpha varied between 30% and 75% and correlated positively with age (P = 0.037). The binding capacity of serum also increased with age. Although men were more frequently positive than women (P < 0.001), there were no sex- or age-dependent alterations in the average affinities of the antibodies. Free IL-1 alpha-like molecules were generally not detected in these sera. However, acid treatment showed that 25% of Ab-IL-1 alpha-positive sera contained low amounts of IL-1 alpha-Ab-IL-1 alpha immune complexes. IgG4 represented the main IgG isotype, whereas IgG3 Ab-IL-1 alpha were undetectable. The relative amounts of IgG4 Ab-IL-1 alpha increased while IgG2-and IgG1 Ab-IL-1 alpha decreased in elderly individuals. The presence in normal individuals and the lack of affinity maturation with age suggest that Ab-IL-1 alpha may be regulatory natural auto-antibodies perhaps coded by germline genes.
Hansen
M B
MB
Department of Infectious Diseases M, Righospitalet, University Hospital, Copenhagen, Denmark.
Svenson
M
M
Abell
K
K
Varming
K
K
Nielsen
H P
HP
Bertelsen
A
A
Bendtzen
K
K
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000936:Antigen-Antibody Complex / Q000097:blood; D001323:Autoantibodies / Q000097:blood*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000145:classification; D007375:Interleukin-1 / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D012737:Sex Factors
D000936:Antigen-Antibody Complex; D001323:Autoantibodies; D007074:Immunoglobulin G; D007375:Interleukin-1