Fidler J M, Howard M C, Shortman K
J Exp Med. 1976 May 1;143(5):1220-38. doi: 10.1084/jem.143.5.1220.
The characteristics of antibody-forming cell (AFC) progenitors lacking previous contact with specific antigen (virgin AFC progenitors) has been studied using sedimentation velocity and buoyant density separation for the investigation of physically distinct B-cell subpopulations. Functional characterization of isolated subsets was made using a quantitative adoptive immune assay for the IgM AFC progenitors responding to the antigen 4-hydroxy-3-iodo-5-nitrophenylacetic acid conjugated polymerized bacterial flagellin. Extensive heterogeneity is present among B lymphocytes, only some subpopulations of which exhibit AFC progenitor function. In the spleen of adult conventional CBA mice, atypically fast sedimenting cells of low buoyant density are active, while typical small B lymphocytes do not appear to be progenitors of IgM AFC. Spleen of adult specific pathogen-free (SPF), germfree, and athymic nude mice give similar results, although a minor population of typical slowly sedimenting dense cells are active in the latter two sources. Adult conventional bone marrow cells are as physically and functionally heterogeneous as splenic B cells, and although a significant proportion of AFC progenitor activity is found among dense, slowly sedimenting cells, most of the activity is among low density, faster sedimenting cells. In contrast to this situation in adult animals, where most of the unprimed AFC progenitors are large, atypical B cells, the spleens of neonatal mice provide a site where virgin AFC progenitors with the physical properties of typical small B lymphocytes are found. While being present in conventional and SPF neonatal spleens, these virgin cells are predominant in 7-day-old germfree mouse spleen. These findings suggest that the newborn virgin B cell is a typical small lymphocyte. However, few cells of this type are found in the adult animal. The unprimed AFC-progenitor population in the adult consists of large, fast sedimenting, low buoyant density, adherent cells, the physical properties of which are characteristic of activated B lymphocytes. It is suggested that these atypical cells are derived from the small newborn virgin B cell by the nonspecific effects of environmental antigenic stimuli.
利用沉降速度和浮力密度分离法研究缺乏先前与特定抗原接触的抗体形成细胞（AFC）祖细胞（未致敏AFC祖细胞）的特性，以调查物理上不同的B细胞亚群。使用针对响应抗原4-羟基-3-碘-5-硝基苯乙酸偶联聚合细菌鞭毛蛋白的IgM AFC祖细胞的定量过继免疫测定法，对分离的亚群进行功能表征。B淋巴细胞之间存在广泛的异质性，其中只有一些亚群表现出AFC祖细胞功能。在成年常规CBA小鼠的脾脏中，浮力密度低的非典型快速沉降细胞具有活性，而典型的小B淋巴细胞似乎不是IgM AFC的祖细胞。成年无特定病原体（SPF）、无菌和无胸腺裸鼠的脾脏给出了相似的结果，尽管在后两种来源中，一小部分典型的缓慢沉降的致密细胞具有活性。成年常规骨髓细胞在物理和功能上与脾B细胞一样具有异质性，虽然在致密、缓慢沉降的细胞中发现了相当比例的AFC祖细胞活性，但大部分活性存在于低密度、快速沉降的细胞中。与成年动物中大多数未致敏AFC祖细胞是大型、非典型B细胞的情况相反，新生小鼠的脾脏提供了一个发现具有典型小B淋巴细胞物理特性的未致敏AFC祖细胞的部位。虽然这些未致敏细胞存在于常规和SPF新生小鼠的脾脏中，但在7日龄无菌小鼠脾脏中占主导地位。这些发现表明新生未致敏B细胞是典型的小淋巴细胞。然而，在成年动物中很少发现这种类型的细胞。成年动物中未致敏的AFC祖细胞群体由大型、快速沉降、浮力密度低的贴壁细胞组成，其物理特性是活化B淋巴细胞的特征。有人认为这些非典型细胞是由环境抗原刺激的非特异性作用从新生小未致敏B细胞衍生而来的。
