Immunoglobulin systems of human tonsils. I. Control subjects of various ages: quantification of Ig-producing cells, tonsillar morphometry and serum Ig concentrations.

Abstract

Specimens of clinically normal palatine tonsils were studied by morphometry and immunohistochemistry, with regard to the relative tissue contribution and the content of Ig-producing immunocytes of four morphological compartments: the germinal centres of lymphoid follicles, their mantle zones, the extrafollicular area and the reticular parts of the crypt epithelium. Ig-producing cells occurred in all compartments; most of them were located in the extrafollicular area, although their density was highest in the reticular epithelium. There was a general predominance of IgG cells—including the blasts present in germinal centres. In subjects 4–25 years old, the tonsillar immunocyte population showed overall IgG:IgA:IgM:IgD class ratios of 65·2:30·1:3·5:1·2. IgE-producing cells were virtually absent. A reticular distribution of non-diffusible immunoglobulins, especially IgM, was observed in the germinal centres—apparently bound to dendritic reticular cells. The mantle zones commonly contained numerous lymphocytes with membrane-related immunofluorescence, particularly prominent for IgD and less distinct for IgM. These B-cells were probably derived from local clonal expansion processes. There was no indication of active immunoglobulin transport through the tonsillar epithelium, which was devoid of `secretory component'. In subjects 30–81 years old, lymphoid elements of the tonsils were reduced, especially the follicular mantles and the reticular crypt epithelium, as well as their content of Ig-producing immunocytes. Such cells were also fewer in the germinal centres and in the extrafollicular area. Moreover, some shifts in the immunocyte class ratios had occurred in the various tissue compartments. In this age group, the number of tonsillar IgA cells showed a significant negative correlation with the rate of synthesis of serum IgA.