Ａ型肝炎におけるＩｇＡ型抗体の動態 Studies on IgA-type antibody in patients with hepatitis A

流行性A型肝炎(HA) 13例,65検体の血中IgA型HA抗体をHAVAB-M kitを応用して測定し,肝炎の経過による同抗体の変動と産生機序について検討した.IgA型HA抗体は発病後第1週より陽性であり,第3週にピークとなり以後漸減した.この変動はIgM型HA抗体と良く平行したが,IgM型と異なり観察し得た第18週においてもなお軽度陽性であった.さらに発病初期血清のIgA型HA抗体の主体はdimer型IgAであった.以上よりA型肝炎感染初期における血清IgA型HA抗体の産生部位は腸管の粘膜下免疫組織であると考えられ,局所免疫応答が密接に関連していると推測された.

The determination of IgA-type antibody against hepatitis A antigen (IgA-type HA antibody) was carried out in 65 sera from 13 patients with hepatitis A by a modified method using anti-IgA coated beads instead of anti-IgM ones in the HAVAB-M kit (Dainabot Co.). The serum IgA-type HA antibody was already detected within 1 week after the onset of symptoms, with maximum levels being observed at approximately 3 weeks after the onset, and then it decreased gradually. These findings were similar to the changes of IgM-type HA antibody, but IgA-type HA antibody was still detectable at 18 weeks after the onset.<BR>In addition, IgA-type antibody in sera proved to be a dimeric form of serum IgA separated by high speed liquid chromatography.<BR>From these results, it was strongly suggested that the intestinal mucosa could play an important role as a major source of serum IgA-type HA antibody at the early stage of HA virus infection.