望从专业知识方面给予解释。

下面这句话来自“IMMUNOMODULATION OF AUTOIMMUNE AND INFLAMMATORY DISEASES WITH INTRAVENOUS IMMUNE GLOBULIN”。红字部分翻译出来也不知什么意思，望从专业知识方面给予解释。

NATURAL ANTIBODIES

Normal serum contains natural antibodies of the IgG, IgM, and IgA isotypes, which are believed to be essential for the immunoregulatory effects of immune globulin in immune-mediated disorders. The antibodies are called “natural” because they are generated in the absence of deliberate immunization and independently of exposure to foreign antigens. 3 Most natural antibodies in healthy people and hence in the immune globulin pool are autoantibodies. Recent evidence indicates that autoantigens stimulate autoreactive B cells to grow and produce natural autoantibodies. 4 The repertoire of natural autoantibodies remains invariable from early childhood through adult life. 5 Most natural autoantibodies in adult serum are of the IgG class, implying that autoreactive T cells contribute to the repertoire of autoreactive B cells under physiologic conditions.

 天然抗体

正常血清中含有IgG、IgM和IgA同种型的天然抗体，这些抗体被认为在免疫介导性疾病中对免疫球蛋白的免疫调节作用是非常必要的。这种抗体之所以被称为“天然”抗体，是因为它们在没有经过刻意免疫且没有接触外来抗原情况下产生的。在健康人群中以及因此在免疫球蛋白库中，大多数天然抗体都是自身抗体。最近的证据表明，自身抗原刺激自身反应性B细胞生长并产生天然的自身抗体。从儿童早期到成年，天然自身抗体的种类保持不变。 5成人血清中大多数天然自身抗体为IgG类，这意味着在生理条件下，自身反应性T细胞有助于自身反应性B细胞的形成。