免疫球蛋白G(IgG)根据其化学结构和功能可分为4种亚类(IgG_1,IgG_2,IgG_3和IgG_4),某种IgG亚类减少或完全缺乏,可引起IgG总量减少,临床表现出反复严重的呼吸道感染,但也可因其它亚类代偿性增高,使IgG总量仍在正常范围,以致错误认为体液免疫未受损害。因为IgG亚类缺乏作为呼吸道感染的原因至今尚未被大多数人所认识,作者报道了4例IgG亚类缺乏所引起的呼吸道感染。 According to its chemical structure and function, immunoglobulin G (IgG) can be divided into four subtypes (IgG_1, IgG_2, IgG_3 and IgG_4). The decrease or complete lack of certain IgG subtype can cause the decrease of total IgG. Repeated severe respiratory infections, but also because of other subclasses compensatory increase, so that the total IgG is still normal range, so mistakenly believe that humoral immunity is intact. Because the absence of IgG subclasses as a cause of respiratory infections has not been recognized by most people so far, the authors report a respiratory infection caused by the absence of four IgG subclasses.