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Previous studies have shown the down-regulating in vitro effect of cocoa flavonoids on lymphocyte and macrophage activation. In the present paper, we report the capacity of a long-term rich cocoa diet to modulate macrophage cytokine secretion and lymphocyte function in young rats. Weaned rats received natural cocoa (4% or 10% food intake), containing 32 mg flavonoids/g, for 3 weeks. Spleen immune function was then evaluated through the analysis of lymphocyte composition, their proliferative response and their ability to secrete cytokines and Ig. In addition, the status of activated peritoneal macrophages was established through tumour necrosis factor (TNF)-α secretion. The richest cocoa diet (10%) caused a reduction of TNF-α secretion by peritoneal macrophages showing anti-inflammatory activity. Similarly, although a 10% cocoa diet increased lymphocyte proliferation rate, it down-regulated T helper 2 (Th2)-related cytokines and decreased Ig secretion. These changes were accompanied by an increase in spleen B cell proportion and a decrease in Th cell percentage. In summary, these results demonstrate the functional activity of a cocoa-high dosage in down-regulating the immune response that might be beneficial in hypersensitivity and autoimmunity. [ABSTRACT FROM AUTHOR]

In this paper we review different aspects of B cell development on the path from the proB cell to the memory B cell and the plasmocyte. Emphasis is given to the positive and negative selection effects mediated by the changing forms of the surface immunoglobulin (Ig) receptor under successive microenvironments. Positive selection is linked to λ chain expression at the pro- and preB cell slage in fetal liver and bone marrow. Negative selection takes place when surface (s)IgM is being cross- linked by autoantigens before the immature B cell can leave, or after it has left, the bone marrow. After somatic mutation, major expansion becomes possible for B cells with high-affinity sIg receptors. This takes place in the germinal centres of the secondary lymphoid organs in the context of major histocompatibility complex (MHC) restriction and provided the necessary T cell help is given. Kinetic data on B cell replenishment in the rodent models are used to draw a schematic view of an established B cell repertoire. [ABSTRACT FROM AUTHOR]

Freshly isolated B cells from chronic lymphocytic leukaemia patients (B-CLL) have been previously shown to induce a strong proliferative response and high levels of NK-like activity in lymphocytes from healthy donors. The present paper deals with the origin, mitotic state, target spectrum and cell surface phenotype of the NK-like effectors generated after stimulation with B-CLL. Experiments using large granular lymphocytes (LGL) and T cells as responders demonstrated that most of the precursors of the newly generated NK-like effectors express the CD3 antigen. The induction of NK-like activity paralleled cell activation, as judged by blast transformation, thymidine uptake and appearance of cell surface activation markers. The newly generated NK-like effectors displayed a T cell phenotype and a broader target repertoire than native NK cells. [ABSTRACT FROM AUTHOR]

IL-2 receptor expression by B cells has previously been considered to be confined to activated normal B cells and, among the B cell leukaemias, to the hairy cells (HC) of hairy-cell leukaemia. In the present paper, using α-Tac monoclonal antibodies in a highly sensitive indirect rosette method, we show that both normal and certain leukaemic B cells other than HC express IL-2 receptors. The density of these receptors is low since they were not detectable by indirect immunofluorescence. Various controls excluded non-specific-reagent or exogenous receptor binding and blocking studies with recombinant IL-2 confirmed the presence of the IL-2 receptors. The significance of the findings is discussed and it is suggested that B cell IL-2 receptor expression without in-vitro activation may be a function of B cell maturity. [ABSTRACT FROM AUTHOR]

The initiation of cytoplasmic Ig synthesis in differentiating B cells is accompanied by the start of cytoplasmic J chain production. As the cell matures further. J chain synthesis ceases (unless it is producing dimeric IgA or 19S IgM). In consequence, it is common to find Ig-positive, J chain-negative cells in reactive lymphoid tissue. However, the reverse pattern (Ig-negative! J chain-positive), which would indicate J chain production unaccompanied by Ig synthesis, has not been reported. In this paper we describe the detection of such cells in reactive human lymphoid tissue by a double immunoenzymatic labelling technique. Furthermore, retrospective immunohistological analysis of 90 cases of human high-grade lymphoma revealed three cases in which the neoplastic cells appeared to synthesize J chain but not Ig. These findings suggest that the term J chain disease might be introduced to describe this new class of lymphoid neoplasm. However, it is pointed out that immunochemical categories of human B lymphoproliferative diseases based upon patterns of Ig synthesis are often in direct conflict with histological categories (cf. mu chain-producing neoplasms) and the term J chain disease cannot therefore be recommended. It is probable that further cases of J chain-positive, Ig-negative lymphoid neoplasms, covering a range of histological categories, will be described in the future. [ABSTRACT FROM AUTHOR]

Peripheral blood lymphocytes from 105 subjects with different forms of leprosy and healthy contacts of leprosy patients were stimulated in vitro with different preparations of mycobacterial antigens alone or in combination with a suboptimal dose of phytohaemagglutinin (PHA). In nearly all individuals sonicated leprosy bacilli and PHA together gave a lower 3H-thymidine incorporation than did the same dose of PHA alone. There was no difference in the degree of inhibition seen in the different patient groups or the healthy contacts. High doses of whole, washed Mycobacterium leprae, combined with PHA led to an increased thymidine incorporation in borderline tuberculoid leprosy patients who had experienced a reversal reaction, and in healthy contacts with more than 6 months of exposure, while most lepromatous patients and contacts with less than 6 months exposure did not show an augmentation of the PHA-induced thymidine incorporation. The inhibition exerted by sonicated M. leprae was dose-dependent, seen even with very low doses of antigen, and was not due to direct cytotoxicity. M. bovis, strain BCG, was weakly suppressive in combination with PHA, and sonicated M. duvalii had a very marked suppressive effect. There was no correlation between the suppressive effect of M. leprue antigens and the other mycobacteria neither was there any correlation with the responses to the mycobacterial antigens alone. Many lepromatous leprosy patients showed significant suppression of background incorporation with addition of M. leprae antigens. This paper discusses whether the apparent `non-responsiveness' in lepromatous leprosy could be due to active suppressor mechanisms operative in vivo. [ABSTRACT FROM AUTHOR]

In previous in vitro studies the DNA synthesis in human blood lymphocytes induced by low concentration of PWM correlated with the percentage of hone marrow-derived (B) lymphocytes in cell suspensions. No correlation with lymphocyte subpopulations was noted when lymphocytes were activated by high concentrations of PWM. In this paper the hypothesis that low concentration of PWM mainly activates B lymphocytes was tested by measuring the (14C]thymidine incorporation into purified T or B lymphocytes from healthy donors. H lymphocytes were purified to 90-95°, by buoyant density centrifugation of T lymphocytes rosetted with sheep red blood cells. T lymphocytes were enriched by passage of lymphocytes through an IgG-anti-IgG-coated column. Low concentration of PWM-stimulated B lymphocytes but not T lymphocytes. while high concentrations of the stimulant activated both cell types. It was also noted that the B- hut not the T-lymphocyte fraction contained cells which synthesized DNA in the absence of PWM. [ABSTRACT FROM AUTHOR]

Mitogen-transformed human peripheral blood lymphocytes and tonsil blasts were examined by rosette formation to detect the presence of membrane-bound immunoglobulin (Ig) and surface receptors for fixed IgG and fixed C3. In addition, the capacity of these cells to rosette with sheep erythrocytes was evaluated as a reaction characteristic of T lymphocytes. In order for clear morphological recognition of the rosetting transformed lymphocytes and the rosetting tonsil blasts a cytocentrifuge technique was developed and used in conjunction with autoradiography and/or with Romanowsky stains. Using these techniques and the culture methods described in this paper phytohaemagglutinin, pokeweed mitogen, streptococcal filtrates and purified protein derivative stimulated predominantly T cells in the peripheral blood of man. A minority of the transformed cells in these mitogen-stimulated cultures (<24%) did rosette with B lymphocyte markers and presumably represent a B-cell response. No significant differences were found between the T- or B-cell specificity of the mitogens investigated. Lymphoid preparations from tonsils excised from normal donors with recurrent tonsillitis were found to contain 6-15% lymphoblasts and the iarge majority of these cells formed rosettes with the B-cell markers, less than 20% of these lymphoblasts formed spontaneous sheep erythrocyte rosettes. Using a mixed rosetting technique a small proportion (<5%) of PHA-transformed cells and tonsil lymphoblasts were found to have combined sheep Fc or combined sheep C3 receptors. The investigation of B- and T-lymphocyte surface markers on mitogentransformed lymphocytes was extended to neopiastic lymphocyte populations and it was found that the majority of transformed cells (>70%) present in chronic lymphocytic leukaemia cultures stimulated with PHA after 6 days incubation were transformed T lymphocytes. [ABSTRACT FROM AUTHOR]