Kinetics of T- and B-lymphocytes in the lymph nodes of human fetuses

Investigations of the lymph nodes embryogenesis had mainly an anatomo-histological character. At the present time a new approach is necessary: elucidation of main immunological characteristics of lymphoid elements, occupying lymph nodes already at early stages of ontogenesis. The aim of the investigation was to study marker composition of lymphocytes, occupying the lymph nodes of various regional groups, that are in anatomical and functional connection with the thymus, Waldeyer-Pirogov lympho-epithelial pharyngeal ring, appendix and Peyer's patches. The anterior, mediastinal, ileocecal and deep cervical lymph nodes have been studied in 23 human fetuses 17-28-week-old. Immunological and morphological peculiarities of development have been followed in the groups of the lymph nodes mentioned. According to the expression of superficial markers the character of heterogeneity in T- and B-cell systems and their kinetics during embryogenesis has been stated to be characteristic for each regional group. In all lymph nodes the number of T-lymphocytes predominate, their greatest content is noted in the ileocecal lymph nodes. The B-lymphatic system in the lymph nodes is presented poorly with its predominance among immunoglobulin-positive lymphocytes of Ig M(+)-cells.     

Studies on the recirculating cells in the mouse thymus

The cells in the mouse thymus which respond to PHA and have the distribution characteristics of recirculating lymphocytes upon infusion into isologous recipients are markedly enriched 2 days after treatment of mice with proper doses of cortisone acetate. However, a similar increase is not observed in lymph nodes and spleen. During regeneration of the steroidinvoluted thymus, the proportion of recirculating thymic cells disappeared more rapidly than the relative PHA-responsiveness of the cell population. These findings indicate that all PHA-responsive thymocytes may not have recirculating capacity. The recirculating cells present in the thymus and lymph nodes have no tendency to distribute to the thymus, but tend to accumulate in lymph nodes. This fact, together with the finding that in vitro trypsin treatment of the cells temporarily abolishes their lymph node-seeking capacity, are taken as evidence that the recirculating cells in the thymus have undergone their maturation within this organ whereby they have gained membrane receptors which determine their distribution characteristics.     

DIFFERENT LABELLING PATTERNS IN MOUSE LYMPHOID TISSUES WITH [3H]DEOXYCYTIDINE AND [3H]THYMIDINE

The percentages of labelled lymphocytes in smear preparations of mouse thymus were higher than those in similar preparations of mesenteric lymph nodes with either generally labelled tritiated deoxycytidine, [³H]CdR, or tritiated thymidine, [³H]TdR. Lymphocytes in the thymus cortex and in germinal centres of mesenteric lymph nodes were intensely labelled with [³H]CdR, whereas with [³H]TdR lymphocytes in the peripheral region of thymus and medullary cords of mesenteric lymph nodes were heavily labelled. The majority of lymphocytes in thymic cortex and germinal centres of mesenteric lymph nodes were labelled weakly with [³H]TdR. Thus, labelling patterns with [³H]CdR differed from those with [³H]TdR in lymphoid tissues of the mouse. Mouse lymphocytes can utilize [³H]CdR as a precursor molecule for cytosine and thymine in DNA. The ratio of radioactivity of thymine to that of cytosine was measured biochemically in DNA extracted from lymphocytes labelled with [³H]CdR. This radioactivity ratio in thymus was higher than that in mesenteric lymph nodes. These results suggest that the metabolic activities of utilizing CdR for DNA synthesis differ within lymphocyte populations in various lymphoid tissues in the mouse.     

降钙素基因相关肽(CGRP)mRNA在大鼠淋巴细胞中的表达

最近,我们研究发现大鼠胸腺和淋巴结淋巴细胞中存在降钙素基因相关肽（ＣＧＲＰ）样免疫反应活性。应用人工合成的可特异扩增降钙素／降钙素基因相关肽基因部分片断的寡核苷酸引物,通过逆转录－多聚酶链反应（ＲＴ－ＰＣＲ）,检测在大鼠脊髓背根神经节、胸腺细胞及肠系膜淋巴结淋巴细胞中是否存在ＣＧＲＰ ｍＲＮＡ,进一步研究大鼠淋巴细胞能否合成ＣＧＲＰ。结果显示,通过ＲＴ－ＰＣＲ从脊髓背根神经节（阳性对照）、胸腺和淋     

Quantitative evaluation of the total number and distribution of lymphocytes in young pigs.

In young pigs, the spleen, thymus and all lymph nodes were dissected out and weighed. The relative content of lymphoid cells was determined from histological sections. The number of nucleated cells was evaluated by two different methods: firstly, by measuring the DNA content of samples of lymphoid tissue and dividing by the DNA content of a single nucleus; and, secondly, by counting all lymphoid cells in histological sections of defined volumes of these organs. The number of lymphoid cells in tonsils, gut, bone marrow and lung were determined using histological evaluations and the volumes or weights of these organs. The resulting average number of lymphocytes was 321 times 10 (9) for a pig of 26 kg body weight. The lymphocytes showed the following distribution in lymphoid and non-lymphoid organs: thymus 44%, spleen 9%, mesenteric lymph nodes 17%, cervical lymph nodes 9%, other peripheral lymph nodes 3%, gut-associated lymphocytes 5%, tonsils 2%, bone marrow 5%, blood 3%, lung 0.2% and an estimated figure of 3% for all other tissues.     

Enhanced suppression of blastogenic responses by weanling mouse lymphoid cells treated with tetrahydrocannabinol in vitro

The suppressive effects of delta 9-tetrahydrocannabinol (THC) on the proliferation of lymphocytes from the spleen, lymph node, and thymus of weanling animals vs adult animals to the T-cell mitogen PHA were examined. THC had a suppressive effect on thymus cells from animals of both younger and older mice. THC suppressed spleen and lymph node cells responses to phytohemagglutinin (PHA) more readily when the cells were obtained from young mice rather than older animals. Suppression by THC in the adult mice was greater in an organ containing fewer mature T lymphocytes such as the thymus in comparison to lymphocytes in secondary organs such as the spleen and lymph nodes which contain more mature lymphocytes.     

Innervation of lymph nodes: a combined silver impregnation and electron-microscopic study

Using silver impregnation and electron-microscopic techniques, nerves have been demonstrated in rat axillary, cervical and inguinal lymph nodes, and their distribution was investigated. With the electron microscope, vesicle-containing varicosities or terminals are demonstrated in close proximity to reticulum cells, lymphocytes, plasmablasts and mature plasma cells. Nerves supplying the blood vessels possibly differ from those supplying stromal or lymphocytic elements.     

B lymphocytes in the guinea pig thymus are specifically localized in the central area.

Since the central area is an integral part of the guinea pig thymus, the cells in this area were compared with those in the thymic cortex and medulla in cryostat-sections by using methods for demonstration of E-, EA-, EAC-adherence and surface membrane immunoglobulins. In the extra cortical central area (ECCA) 15 to 25% of the lymphocytes showed EAC-adherence and 5 to 10% appeared to bear surface membrane immunoglobulins (SIg). In the lymph sinuses up to 70% of the lymphocytes were EAC- and SIg-positive. A small amount of EAC-adhering cells was present in the medulla of the central area. Cortical lymphocytes were EAC- and SIg-negative. From these results we conclude that in the guinea pig thymus B lymphocytes are specifically localized in the central area.     

The functional capabilities of cells leaving the thymus

There has been a controversy for many years over the functional status of cells that leave the thymus (thymus migrants) to populate the peripheral lymphoid organs. Are they immunoincompetent like cortical thymocytes and so probably derived from them, or are they functionally mature like medullary thymocytes? Until recently the techniques used to assess putative thymus migrants have been indirect, but it is now possible to measure the function of recent thymus migrants directly. We used intrathymic injection of a solution of fluorescein isothiocyanate to label thymocytes, and used electronic cell sorting to purify the fluorescent cells that accumulate in the periphery over the following 3 to 4 hr. The migrants have been enriched from an original frequency of about 1:1000 in lymph nodes and spleen, to greater than 98% purity. These cells have been compared with normal peripheral T cells for proliferative and cytotoxic precursor activity in a high cloning efficiency, lectin-induced, limit dilution culture system and in an allospecific limit dilution system. The frequency of precursors of proliferative lymphocytes and cytotoxic lymphocytes and the size of the clones produced is the same for recent migrants and peripheral T cells. Thus by the criteria of proliferation and cytotoxic responses to mitogens and generation of allospecific CTL, thymus migrants, a few hours after their emigration from the thymus, are fully immunocompetent; we therefore see no evidence of a post-thymic precursor-type cell that requires major maturation steps after leaving the thymus.     

Distribution and ultrastructure of S-100-immunoreactive cells in the human thymus

Summary The present study deals with the localization and ultrastructure of S-100-immunoreactive cells in the human thymus. These immunoreactive cells are distributed mainly in the medulla with some scattered elements in the cortex. Electron-microscopic observation revealed that the cells are characterized by an irregularly shaped nucleus, tubulovesicular structures in the cytoplasm and characteristic interdigitations of the plasma membrane. The cells often embrace lymphocytes with their branched processes. On the basis of these morphological features, the immunostained elements were identified as interdigitating cells (IDCs). The immunocytochemistry for S-100 visualizes the precise distribution and extension of the IDCs under the light microscope and indicates that the IDCs form no structural networks such as those established by the thymic epithelial cells. Since the IDCs in human lymph nodes have also been reported to contain S-100-like immunoreactivity, S-100 protein can be regarded as a useful marker for identifying the IDCs in the human thymus and other lymphoid organs.     

STUDIES ON LYMPHOCYTES

Tritiated thymidine was administered to calves continually for 2 to 8 days via the thymic artery in an attempt to label intensively thymic lymphocytes. Heavily labeled cells which had migrated from the thymus were observed in the spleen, lymph nodes and Peyer's patches. Cell maps were made for the various lymphoid tissues and in all cases the majority of labeled thymic cells were found in the ‘thymus dependent areas’of the spleen and lymph nodes. The number of labeled thymic cells per thousand lymphocytes was highest in the ‘thymus dependent areas’. A few labeled thymic cells were seen in or near the post capillary venules. The labeling pattern in the Peyer's patches was different from that in the spleen and lymph nodes. Labeled thymic cells were not observed in the bone marrow. Heavily labeled cells were not detected in any of the lymphoid tissues of those calves which received continuous intravenous infusion of comparable amounts of tritiated thymidine.     

Changes in the rat lymphoid organs in acute hypoxia

Changes occurring in the rat thymus, spleen, mesenteric lymph nodes have been studied by means of some histological and cytofluorimetrical methods under the effect of an acute hypoxia that imitates the rise to 7,000 m above the sea level for 1 h and to 6,500 m for 6 h. Under the effect of hypoxia, migration of differentiated lymphocytes out of the lymphoid organs is increasing, certain essential shifts in temporal parameters take place in the mitotic cycle of the lymphocytes, contents of nucleic acids in the lymphoid cells change. The phenomena mentioned demonstrate that under the acute hypoxic stress, intensified differentiation processes of the lymphocytes in the thymus, spleen and the lymph node take place and the lymphoid tissue functional activity increases.     

Reaction of human lymphocytes with aggregated IgG columns. Effect on antibody-dependent cytotoxicity and EAC rosette formation.

The origin and life span of long-lived small lymphocytes in the bone marrow of mice have been evaluated by the use of radioautography, scintillation counting, and anti-theta serum. Thymus-deprived BALB/C mice and nude mice had a smaller percentage of long-lived lymphocytes in bone marrow and in thoracic duct lymph than sham-operated or normal littermates. Furthermore, the long-lived lymphocytes in the marrow of nudes have more varied—but generally shorter—life spans than long-lived lymphocytes from mice having a thymus. In thoracic duct lymph of nude mice a more homogeneous long-lived population—according to life span—was found.It was concluded that both long-lived T cells and long-lived B cells are normal residents in the bone marrow. Furthermore, it was concluded that cells of variable life spans comprise the B lymphocyte population: short-lived cells with life spans of 3–5 days and long-lived lymphocytes with life spans of weeks to months.     

Ganglioside composition of normal and leukemic bovine lymphocytes

The ganglioside composition of bovine peripheral lymphocytes was shown to change sharply under lymphoid leukemia. In normal lymph, lymph nodes, spleen and blood lymphocytes the major ganglioside is N-glycolylhematoside, whereas in calf thymus lymphocytes appreciable amounts of more polar components (GM1- and GD1a-like gangliosides) were found. In leukemic lymphocytes isolated from the same tissues the hematoside content is decreased, while the amount of more polar gangliosides is increased. Possible causes of the altered ganglioside pattern in leukemic lymphocytes are discussed.     

Synergy among rat T cells in the proliferative response to alloantigen.

A synergistic interaction in the proliferative response to alloantigen is described for mixtures of rat thymus and lymph node cells. The optimal conditions for synergy are quantitatively defined. Regression analysis of the slope of the dose-response curve has been utilized to estimate the degree of interaction in thymus-lymph node cell mixtures. The slope of the response of cell mixtures was noted to be significantly greater than the slope for the response of lymph node cells alone. Irradiation was shown to have a differential effect on the response of thymus and lymph node cells in mixtures. Irradiated thymus cells retained the capacity for synergy in mixtures, whereas irradiated lymph node cells did not. Additional studies have demonstrated that both de novo protein synthesis and specific antigen recognition by both responding cell populations in mixtures was required for maximal synergy. These studies demonstrate that synergy cannot be explained as an artifact of altered cell density in vitro. They establish that thymus cells and lymph node cells represent distinct subsets which manifest qualitatively different functions in the proliferative response to alloantigen. Thymus cells can respond directly to alloantigen by proliferation but also have the capacity to amplify the proliferative response of lymph node cells—a capacity which is resistant to X irradiation but requires recognition of alloantigen and de novo protein synthesis. Lymph node cells may similarly respond by proliferation to alloantigen but lack the amplifier activity of thymus cells. Synergy for rat lymphoid cells, like mouse lymphoid cells, has been shown to involve an interaction of thymus-derived lymphocytes.     

The Functions of the Thymus

In rodents the thymus performs at least two functions. It is a major site of lymphopoiesis in the embryo and newborn, with the resulting lymphocytes migrating from the thymus to seed the spleen, lymph nodes and other lymphoid organs. In addition, the thymus produces a hormone which has an immunotrophic effect, i.e. it endows cells having immunological potential with immunological competence. In some animals other organs, in addition to the thymus, are responsible for directing the normal development of the immunological system. These are the bursa of Fabricius in birds and the appendix in rabbits. In humans it has been postulated that the tonsillar tissues may play an analogous role. Animal experiments involving extirpation of the immunotrophic lymphoid tissues have led to a better understanding of immunological deficiency diseases in man.     

Extrathymic rearrangement of αβT-lymphocyte antigen receptor genes during pregnancy

The existence of alphabetaT-lymphocyte differentiation processes have been demonstrated in mouse peripheral lymphoid organs during pregnancy. Study of pregnant Swiss mice has shown that the development of the second half of gestation is accompanied by expression of RAG-1 recombinase mRNA and unrearranged TCR alpha-chain (pre-TCRalpha) preferentially in T-lymphocytes of lymph nodes involved in uterine drainage (para-aortal lymph nodes), and to a lesser extent in other lymph nodes (mainly from axillary lymph nodes). The data suggest that during pregnancy the differentiation of alphabetaT lymphocytes may occur not only in central (thymus) but also in peripheral lymphoid organs.     

New Ideas on Amphibian Immunity: The Lymph Gland: A Generator of both T and B Cells

Anuran amphibian larvae of the genus Rana possess three majorlymphoid organs: the thymus, the lymph gland, and the spleen.Other accumulations of lymphocytes are present in the kidney,liver, and intestine. The thymus develops lymphocytes firstfollowed by peripheral differentiation of other lymphoid centers.Since bone marrow is absent in larvae, there must be an alternativesource of stem cells that differentiate into T cells under thymicinfluence or B cells under the influence of some other organ(s).We are concerned with the source of B cells after bullfrog larvaebecome immunologically mature. Such an organ should possessstem cells, and, to qualify further, it should play a majorrole in antibody synthesis. The lymph gland seems to fulfillthis requirement. Contrary to our expectations, lymph glandscan restore not only antibody synthesis but also transplantationimmunity in a significant number of larvae. Thus, the lymphgland may house stem cells that can differentiate into B cellsand T cells.     

cytophotometric,flow cytofluorometric and morphometric demonstration of the existence of an antigen dependent thymus lymphocyte subpopulation

Summary Using absorption cytophotometry and flow cytofluorometrical DNA and protein estimation of single thymus lymphocytes we were able to establish that after injection of a large dose of antigen (ovalbumin) a subpopulation of lymphocytes arises in the thymus with high protein contents above that of those lymphocytes normally present, however, in small quantities in the thymus. By morphometrical analysis it was established that these lymphocytes are situated in the outermost cortex.     

Comparative study of the T- and B-cell immunity systems in human and animal embryogenesis

Data are presented on the spleen and thymus structure, time of appearance of the lymphocytes and their heterogeneity in the liver, thymus, spleen, lymph nodes and blood of human foetuses with hemochorial placenta (3 to 34 weeks) and of the minipigs foetuses with epitheliochorial placenta (32 to 95 days). In both foetuses the first T- and B-lymphocytes are found in liver, T-lymphocytes are then found in thymus and later in spleen and lymph nodes whereas B-lymphocytes are found, after liver, in spleen. Kinetics of T- and B-lymphocytes during embryogenesis is described. Reaction of the minipig lymphocytes to mitogens was demonstrated.