Mouse Thymus-Independent and Thymus-Derived Lymphoid Cells

Abstract

The ultrastructural features of B-, T-, and surface Ig(sIg)-bearing cells have been studied on cell suspensions from lymphoid organs of mice at different stages of immunization. The cells were identified by exposure to rabbit antibodies against mouse-specific lymphocyte antigens (MSLA) or brain-associated θ antigen (BAθ) for T cells, mouse-specific bone marrow-derived lymphocyte antigens (MBLA) for B cells, and mouse Ig for sIg-bearing cells. The rabbit antibodies fixed on the cell surfaces were detected by peroxidase-labeled sheep anti-rabbit Ig antibodies or by a "bridge" technique using southern bean mosaic virus or bacteriophage T4 as the final markers. In some experiments, short-lived lymphoid cells were labeled in vivo with repeated tritiated thymidine and the ultrastructural detection of their surface antigens was combined with radioautography. MBLA+ lymphoid cells showed a whole range of ultrastructural patterns. Most were small and medium-sized lymphocytes with a clear cytoplasm containing mono- and polyribosomes, but they comprised also blasts and large cells with various amounts of endoplasmic reticulum, as well as plasma cells at different stages of maturation. sIg-bearing cells appeared to be identical with MBLA+ cells, except that sIg was less easily detectable on large blasts, and only very rarely observed on plasma cells. MSLA+ and BAθ+ cells fell into three categories. One of them (T1 cells) consisted of small to medium-sized lymphocytes with a clear cytoplasm and few organelles, mostly monoribosomes. A second consisted of large cells (T2 cells) characterized by numerous polyribosomes often in a "rosette"-like pattern, occasional dark, membrane-bound granules, and a developing "filamentous network." The third, very characteristic type, (T3 cells) was represented by dark small to medium-sized lymphocytes, usually containing large amounts of closely packed ribosomes and showing a striking accumulation of filamentous network, often condensed in large areas devoid of cell organelles. This filamentous network appeared to correspond to the cytochalasin B-sensitive system of microfilaments found in other cells and considered to be one of the contractile elements of the cell. The T3 lymphocytes showed frequently vesicles suggestive of a strong pinocytic activity, and assumed a variety of shapes, including uropods. Evidence is presented that T1 lymphocytes represent "virgin" T cells, T2 "activated," and T3 "differentiated" lymphocytes.

Human T and B Lymphoid Cells

“…The ultrastructural variety of lymphocytes within the T or B cell population might depend on their place in the differentiation pathway, which is little understood in humans but was studied in experimental animals (GUDAT et al, 1971 a, b;MATTER et al, 1972). Large lymphocytes containing relatively abundant rough endoplasmic reticulum probably represent a transitional form to plasma cells (ZUCKER-FRANKLIN, 1969;GUDAT et al, 1971 a, b).…”

The surface morphology of human B lymphocytes as revealed by immunoelectron microscopy.

“…In this study, the latter possibility is ruled out since control experiments with normal conjugated rabbit y-globulins gave constant negative results. An alternative hypothesis would be a "false" labeling of contiguous cells by flowing of the enzymatic reaction product from positive lymphocytes (6) . This seems improbable here since labeled monocytes were found which were not contiguous to B lymphocytes and conversely cells in close contact were devoid of surface staining (Fig .…”

“…To date no major morphological distinction of the surface of mammalian lymphocytes has emerged from immunoelectron microscopic studies using the autoradiography technique (4, 5, 21), virus (22), ferritin (23)(24)(25), or peroxidaseconjugated antibodies (3,6,26) . However, it can be noticed that these experiments have been carried out on living cells, thus allowing some surface redistribution and endocytosis of reagents, as a result of membrane activation (26)(27)(28) .…”

Elektronenmikroskopische Lokalisation von Thiaminpyrophosphatase und Nucleosiddiphosphatase in Lymphozyten

“…Demgegenüber sind NDPase-positive Zellen überwiegend kugelige Lymphozyten ohne starke Gliederung der Zellmembran (Abb. 5), entsprechend den T-ZellMerkmalen [20,21,27]. Ob diese Befunde an definierten B-bzw.…”