Immunoglobulin determinants on the surface of human lymphocytes

B lymphocytes: how they develop and function

The discovery that lymphocyte subpopulations participate in distinct components of the immune response focused attention onto the origins and function of lymphocytes more than 40 years ago. Studies in the 1960s and 1970s demonstrated that B and T lymphocytes were responsible primarily for the basic functions of antibody production and cell-mediated immune responses, respectively. The decades that followed have witnessed a continuum of unfolding complexities in B-cell development, subsets, and function that could not have been predicted. Some of the landmark discoveries that led to our current understanding of B lymphocytes as the source of protective innate and adaptive antibodies are highlighted in this essay. The phenotypic and functional diversity of B lymphocytes, their regulatory roles independent of antibody production, and the molecular events that make this lineage unique are also considered. Finally, perturbations in B-cell development that give rise to certain types of congenital immunodeficiency, leukemia/lymphoma, and autoimmune disease are discussed in the context of normal B-cell development and selection. Despite the significant advances that have been made at the cellular and molecular levels, there is much more to learn, and cross-disciplinary studies in hematology and immunology will continue to pave the way for new discoveries.

Genetic analysis of patients with defects in early B-cell development

Approximately 85% of patients with defects in early B-cell development have X-linked agammaglobulinemia (XLA), a disorder caused by mutations in the cytoplasmic Bruton's tyrosine kinase (Btk). Although Btk is activated by cross-linking of a variety of cell-surface receptors, the most critical signal transduction pathway is the one initiated by the pre-B cell and B-cell antigen receptor complex. Mutations in Btk are highly diverse, and no single mutation accounts for more than 3% of patients. Although there is no strong genotype/phenotype correlation in XLA, the specific mutation in Btk is one of the factors that influences the severity of disease. Mutations in the components of the pre-B cell and B-cell antigen receptor complex account for an additional 5-7% of patients with defects in early B-cell development. Patients with defects in these proteins are clinically indistinguishable from those with XLA. However, they tend to be younger at the time of diagnosis, and whereas most patients with XLA have a small number of B cells in the peripheral circulation, these cells are not found in patients with defects in micro heavy chain or Igalpha. Polymorphic variants in the components of the pre-B cell and B-cell receptor complex, particularly micro heavy chain and lambda5, may contribute to the severity of XLA.

[Lymphocyte subpopulations in the normal cerebrospinal fluid: I. Major reports in the literature]

Data concerning the characterization of lymphocytes in the cerebrospinal fluid are reviewed, markedly those on T and B subpopulations. Special attention is given to T-lymphocyte subpopulations actually related to the immune response and to the immune regulation within the central nervous system.

The mixed antiglobulin rosetting reaction (MARR) and the direct antiglobulin rosetting reaction (DARR): sensitive tests for demonstration of immunoglobulin-bearing B lymphocytes

The technology of the mixed antiglobulin rosetting (MARR) and the direct antiglobulin rosetting reaction (DARR) is reviewed. These tests have been found to be more sensitive than the standard direct immunofluorescence (DIF) method for delineation of Ig-bearing B lymphocytes and to have practical advantages over DIF. Further, with these rosette tests, an important B lymphocyte population has been identified which is Ig-negative by DIF and functionally quite different from typical DIF-positive B lymphocytes but which expresses a low density of surface membrane Ig that is detectable by the MARR and the DARR.

Technical improvements in the mixed antiglobulin rosetting reaction with consequent demonstration of high numbers of immunoglobulin-bearing lymphocytes in viable preparations of human peripheral blood

A modification of the mixed antiglobulin rosetting reaction (MARR) to improve sensitivity as a test for immunoglobulin (Ig)-bearing human blood lymphocytes is described. A mean 5.7%, lymphocytes Ig-positive by the MARR when rosettes were formed in medium containing 0.2% bovine serum albumin (BSA), increased to 20% when rosettes were formed in 5% BSA or by incubating the lymphocytes or indicator erythocytes with Vibrio cholerae neuraminidase before rosetting. Under these various rosetting conditions the MARR is as sensitive as the direct antiglobulin rosetting reaction (DARR). Further, with the MARR, false positive rosette formation due to unusual antimembrane antibodies can be excluded during the mixed antiglobulin rosetting procedure by use of blocking controls. Substitution of F(ab)2 antiglobulin for IgG anti-gamma, anti-alpha and anti-mu did not reduce the number of lymphocytes demonstrable with the MARR, indicating that the MARR does not react with adsorbed Ig molecules on lymphocytes. Summation of the number of sheep erythrocyte (E) rosetting lymphocytes and mixed antiglobulin rosetting lymphocytes approximated 100%, yet in T-enriched preparations a maximum of 4% of lymphocytes were Ig-positive by the MARR, suggesting that null lymphocytes which have been reported to be E-negative and immunofluorescence-negative are B lymphocytes with surface Ig determinants.

Immunological and functional characteristics of peripheral blood and synovial fluid lymphocytes from patients with rheumatoid arthritis

Spontaneous (SCMC) and antibody dependent cellular cytotoxicity (ADCC); mitogenic responsiveness (PHA, Con A, PPD, dextran and pokeweed) as well as lymphocyte subpopulations (E-, EA-, EAC-rosettes, S-Ig) were studied simultaneously in peripheral blood (PBL) and synovial fluid lymphocytes (SFL) of fifteen patients with rheumatoid arthritis. Marked differences were observed in the cytotoxic activity of SFL and PBL. Whereas SCMC activity of SFL was always significantly elevated above the cytotoxic levels of PBL, the reverse was true for the ADCC reaction; here, 50% of the patients showed a decreased cytotoxicity of SFL compared to PBL. Synovial fluid neutrophils (SFN) were found to be inactive in both cytotoxic assays. No differences were found in ADCC activity of PBL between normal controls and RA patients. In SCMC assays a significantly increased activity of control PBL was only observed at L/T ratios of 100:1. Overnight incubation of PBL from RA patients and normal controls resulted in a marked decrease in SCMC and, to a smaller extent, in ADCC activity. SFL from three out of four patients lost less SCMC activity after overnight incubation than the corresponding PBL. In one patient even an increased activity in both cytotoxic systems was obtained. Regarding lymphocyte populations, T-cells were significantly decreased in PBL of RA patients. With the exception of a significantly lowered percentage of C3 receptor positive cells in SFL, no significant differences were recorded in the lymphocyte distribution between the patients' PBL and SFL. In the RA patients, the response to T-cell mitogens was significantly depressed in SFL while PPD and pokeweed reactivity was equal to that of PBL.

Ultrastructural labeling of lymphocyte surface immunoglobulin: the preparation and use of soluble immune complexes as indirect immunoelectromicroscopic markers

2 distinct macronuclear markers, ferritin and hemocyanin, may be used in a mixed anti-globulin labeling reaction to localize lymphocyte surface immunoglobulin (Ig) determinants by transmission electron microscopy. Soluble immune complexes of the marker molecules (antigen) are prepared by complexing with specific antiserum in 40 to 50 x antigen excess; uncomplexed Ig is removed by ultrascentrifugation and/or gel filtration chromatography. Immunoelectrophoresis, spectrophotometry and passive hemagglutination inhibition assay are used to determine the purity and amounts of antibody-antigen in the purified immune complexes. For immunoelectron microscopic labeling, the immune complex markers are coupled to lymphocyte surface Ig by an indirect anti-Ig or anti-allotype antibody linkage. Labelled Ig determinants at 0 degrees C or in the presence of sodium azide are visualized as small patches of marker molecules on the lymphocyte surface membrane. This EM labeling method results in much more consistent and generally higher percentages of surface Ig positive cells (60 to 70% of rabbit peripheral blood lymphocytes) than the percentages obtained using other methods, such as immunofluorescence or autoradiography. If the lymphocytes are warmed to 37 degrees C in the absence of azide the labeled surface Ig determinants undergo rapid endocytosis; endocytotic vesicles containing marker molecules are visible. This mixed anti-globulin immunoelectronmicroscopic labeling system may be used to localize a wide variety of antigens on different cell surfaces.

Distribution of B, T, and O lymphocytes in blood and tissues of normal humans reflecting a kinetic model

The occurrence of the lymphocyte subpopulations TE, BFc, BC3, BFc + C3, BIg, and O-, percentage as well as absolute, was studied in lymphocyte suspensions from tonsils, abdominal lymph nodes, spleens, bone-marrow aspirates, and at the same time in venous blood. The absolute lymphocyte content (number of lymphocytes per g tissue) was highest in the abdominal lymph nodes, lower in the spleens and tonsils, and lowest in the blood. TE lymphocytes were found in the significantly highest percentage, 60%, in the blood. B lymphocytes, comprising BFc + C3 plus BIg, were present in the highest percentage in the bone marrow: 74%. Tonsils, spleens, and abdominal lymph nodes contained fewer B lymphocytes, and the blood fewest: 39%. A significant correlation was found only between the absolute numbers of T and B lymphocytes. A relationship between the absolute number of T lymphocytes and the total number of B lymphocytes as well as fractions thereof was thus demonstrated in the various tissues and in the blood and also between the blood and the tissue. O- lymphocytes were found in bone marrow, lymph nodes, and spleens, apparently as markerless precursors of other subpopulations. The main conclusion of the study is: In the lymphocytokinetic system the T lymphocytes must play a guiding role as an afferent vector, trigging the B fractions which thus constitute the efferent vector of the system.

Lymphocyte surface immunoglobulins: detection, characterization, and occurrence in disease of the lymphoid system

Surface immunoglobulins (Igs) of lymphocytes are of considerable interest because these molecules probably function as receptors for antigen, and knowledge of their molecular properties should provide information on the mechanisms of immune differentiation. The density and types of surface Ig on a cell provide markers useful in indicating the class of a lymphocyte and its stage of maturity. Moreover, knowledge of the specificities of the surface Ig of neoplastic lymphocytes might suggest the nature of agents involved in the generation of the disease. Two broad classes of lymphocytes, bone marrow-derived lymphocytes (B cells) active in antibody secretion, and thymus-derived lymphocytes (T cells) which mediate cellular immune reactions, and their subpopulations must be considered with reference to the nature, origin, and function of their surface immunoglobulin. This article analyzes direct and indirect methods for the demonstration of surface Igs and describes certain physicochemical properties of isolated surface Ig molecules. Roles of these surface molecules in recognition of antigen, initiation of all differentiation, and cooperation among lymphocytes and accessory cells are discussed.

Immunological characterization of lymphoproliferative disorders by membrane markers

The characterization of lymphocyte subpopulations by means of surface markers improved our understanding of the immunopathology of lymphoproliferative disorders. In chronic lymphocytic leukemia an accumulation of B-lymphocytes have been documented. The antibody deficiency syndrome in these patients might well reflect a maturation defect of the leukemic B-lymphocytes. In patients with Hodgkin's disease the relative number of B- and T-lymphocytes in the blood was not markedly altered in comparison to normal controls. An increased proliferation primarily of T-lymphocytes however, might suggest their accelerated turnover as an indication of the host response. In most patients with "Non-Hodgkin" lymphomas high numbers of B-lymphocytes were found in affected lymph nodes, and these appear occasionally in the peripheral blood. Differences in immunopathological manifestations of the various subgroups of the "Non-Hodgkin" lymphomas are emphasized and the rare occurrence of lymphomas of T-lymphocytes (mainly observed in lymphoblastic lymphomas and in Sézary syndrome) is discussed. Immunopathological alterations in immunocytomas and the myelomas are considered in respect to the involvement of B-lymphocytes at different stages of maturation.

In vitro induction and measurement of hemolytic plaque forming cells in man

Following co-cultivation with sheep red cells or ovalbumin, Hypaque-Ficoll-separated human tonsillar lymphocytes were demonstrated to generate specific hemolytic PFC with maximum numbers at day 5-7. PFC were enumerated on poly-L-lysine coupled red cell monolayers in Microtest-II-plates. Plaque formation appeared to be puromycin-sensitive, complement-dependent and showed clear specificity for the antigen present during the inductive culture. Treatment of PFC with mu-chain specific antisera and complement resulted in complete inactivation of PFC; gamma-chain antisera had no effect. The development of such a simple and sensitive assay system permits the analysis of cellular interactions required for the induction of PFC responses in man.

Differentiation capacity of cultured B lymphocytes from immunodeficient patients

Peripheral blood lymphocytes from 27 healthy individuals and from 18 patients with a diverse spectrum of defects in humoral immunity were examined for their capacity to undergo terminal differentiation in vitro. Pokeweed mitogen induced cells from normal persons to synthesize and secrete IgM. IgG, and IgA as detected by Immunofluorescence and incorporation of [(14)C]amino acids, Lymphocytes from three boys with X-linked agammaglobulinemia were stimulated to proliferate, but did not synthesize immunoglobulin. Lymphocyte cultures from three of four patients having agammaglobulinemia with B lymphocytes produced different immunoglobulin classes in ratios similar to the in vivo distribution of classes of B lymphocytes, Lymphocytes from a dysgammaglobulinemic boy deficient in serum IgG and IgA, but who had normal numbers of IgM-, IgG-, and IgA-bearing B lymphocytes, could not be stimulated by pokeweed mitogen to make IgG and IgA. Synthesis and secretion of IgA, as well as IgM and IgG, was detected in cell cultures from each of 10 patients with isolated IgA deficiency. The results suggest that deficiencies in immunoglobulin synthesis may reflect either (a) failure to develop B lymphocytes, (b) arrested development of B lymphocytes due to intrinsic metabolic abnormalities, or (c) disturbance of factors extrinsic to the B lymphocyte which are essential for normal induction of plasma cell maturation.

Electron microscope study of surface immunoglobulin-bearing human tonsil cells

Surface immunoglobulin-bearing cells were selected from suspensions of human tonsil cells by the reverse immune cytoadherence technique. The method employed a hybrid antibody directed against Ig on lymphoid cells and against ferritin bound to sheep red blood cells (SRBC). Only 6% of the cells formed rosettes. When subjected to electron microscopy they were shown to consist of a morphologically heterogeneous population of cells. However, most cells in the center of rosettes showed ribosome-associated endoplasmic reticulum (RER) and polyribosomes. Usually these organelles were located in close proximity to membrane sites where a 400-600 A bridge was resolved between the lymphocyte and the ferritin particle on the SRBC. The bridge is postulated to consist at least in part of Ig. Only 50% of the plasma cells formed rosettes and bridges could not be resolved. The surface of the plasma cells within rosettes differed from that of plasma cells which had not reacted with ferritin-coated sheep erythrocytes. The incidence of plasma cells and gamma-globulin-bearing lymphoid cells was corroborated with the help of fluorescent antibody techniques.

Regulation of the immune system by synthetic polynucleotides. V. Effect on cell-associated immunoglobulin receptors and immunological memory

Addition of polyadenylic-polyuridylic acid in complex form (poly A:U) without antigen to a suspension of spleen cells obtained from BALB/Aj mice primed 6 wk previously with human gamma-globulin (HGG) resulted in an immediate fourfold increase over background number of anti-HGG rosette-forming cells (RFC). Culture of similar cells in the presence of puromycin for 1-6 hr before poly A:U did not significantly reduce the response. Continued culture of primed spleen cells in the presence of poly A:U, resulted in a decrease of RFC to background levels within an hour followed by an increase again 6 hr later. This later increase in RFC was inhibited by addition of puromycin to the culture medium. The nonspecific stimulation by poly A:U of antibody production by primed spleen cells also was induced in vivo. Increases in splenic RFC were detectable 6 hr after intravenous injection of poly A:U alone, without antigen, into primed mice. The response peaked at 18 hr and had dissipated completely within 3 days. A second injection of poly A:U 24 hr or later after the first injection resulted in a second response, similar to the first with respect to kinetics and intensity. Rosette formation by poly A:U-stimulated cells could not be inhibited by mitotic poisons, but was inhibited by treatment of the cells with goat anti-mouse gamma-globulin serum, suggesting that the antibody involved was a 7S gamma-globulin. The decrease in RFC induced by culture of primed cells for 1 hr in poly A:U paralleled a decrease in secondary responsiveness of the cells to antigen. This poly A:U-induced inhibition of secondary responsiveness could be reversed by suspending the treated cells in supernatant fluids derived from poly A:U-stimulated cultures. The reversal was specific in that supernatant fluids removed from bovine serum albumin (BSA)-primed cells by poly A:U did not stimulate the response of HGG-primed cells to HGG. However supernatant fluids from BSA-primed cells caused the production of anti-HGG RFC if BSA rather than HGG was used as triggering antigen. The active factor in the supernatant fluids appeared to be a 7S gamma-globulin since activity was lost after 45 min incubation of the supernatant fluids in the presence of goat anti-mouse 7S gamma-globulin serum.