Immunoglobulins as cell receptors

A transcriptional serenAID: the role of noncoding RNAs in class switch recombination

During an immune response, activated B cells may undergo class switch recombination (CSR), a molecular rearrangement that allows B cells to switch from expressing IgM and IgD to a secondary antibody heavy chain isotype such as IgG, IgA or IgE. Secondary antibody isotypes provide the adaptive immune system with distinct effector functions to optimally combat various pathogens. CSR occurs between repetitive DNA elements within the immunoglobulin heavy chain (Igh) locus, termed switch (S) regions and requires the DNA-modifying enzyme activation-induced cytidine deaminase (AID). AID-mediated DNA deamination within S regions initiates the formation of DNA double-strand breaks, which serve as biochemical beacons for downstream DNA repair pathways that coordinate the ligation of DNA breaks. Myriad factors contribute to optimal AID targeting; however, many of these factors also localize to genomic regions outside of the Igh locus. Thus, a current challenge is to explain the specific targeting of AID to the Igh locus. Recent studies have implicated noncoding RNAs in CSR, suggesting a provocative mechanism that incorporates Igh-specific factors to enable precise AID targeting. Here, we chronologically recount the rich history of noncoding RNAs functioning in CSR to provide a comprehensive context for recent and future discoveries. We present a model for the RNA-guided targeting of AID that attempts to integrate historical and recent findings, and highlight potential caveats. Lastly, we discuss testable hypotheses ripe for current experimentation, and explore promising ideas for future investigations.

Isolation and chemical characterization of the human B29 and mb-1 proteins of the B cell antigen receptor complex

A disulfide-linked heterodimeric antigen from human B leukemia cells was detected by radioimmunoprecipitation and Western blot analysis using a monoclonal antibody (mAb). The mAb was generated against a cell membrane antigen preparation from human B prolymphocytic leukemia cells and found to define an extracellular epitope of the smaller component (beta chain) of a heterodimeric antigen on human B leukemia cells. The antigen from BALL-1, a human B leukemia cell line, and fresh (uncultured) B prolymphocytic leukemia cells was found to consist of a 44-49 kDa (alpha chain) and a 36-40 kDa (beta chain) component. An additional minor component of 34 kDa was detected in the reduced antigen from BALL-1. For chemical identification of the antigen, we isolated the antigen from a Triton X-100 lysate of BALL-1 by immunoaffinity chromatography using the mAb. Determination of the amino-terminal amino acid sequences of the alpha and beta chains unequivocally identified them as the human mb-1 and B29 proteins, respectively. The sequence analyses indicate the molecular heterogeneity of the mb-1 protein and also perhaps the heterogeneity of the B29 protein. We detected three forms of the mb-1 protein which share an identical amino-terminal amino acid sequence and probably two forms of the B29 protein which share an identical amino-terminal sequence. Our sequence data allowed us to establish the authentic amino-terminal amino acid sequence of the human B29 protein which is different from those proposed by others based on cDNA sequence analyses. Comparison of the amino-terminal sequences of the human mb-1 and B29 proteins with those of the mouse mb-1 and B29 proteins showed that the majority of the conserved amino acids in the mb-1 proteins are hydrophobic amino acids. Such conservation of hydrophobic amino acids is not observed in the amino termini of the human and mouse B29 proteins. A beta-tubulin-like protein was found to be co-purified with the mb-1-B29 antigen in the present study. In addition, we found that there is a strong amino acid sequence homology between the microtubule-binding domains of certain human microtubule-associated proteins and an intracellular segment of the human mb-1 protein.

Extensive splenic B cell activation in IgM-transgenic mice

Two lines of IgM-transgenic mice were analyzed for the state of activation of their splenic compartment, with regard to the frequency of large cells in the different lymphoid subpopulations, and to the isotype distribution of background plasma cells. We observed an extensive B cell activation preferentially involving B lymphocytes co-expressing transgenic and endogenous IgM (IgD), and resulting in massive immunoglobulin class switch. Nearly all splenic plasma cells contain endogenous immunoglobulins, with frequencies of IgG and IgA plasma cells significantly higher than in normal mice. There are virtually no plasma cells that produce only the transgenic IgM. Moreover, only a proportion of plasma cells producing endogenous immunoglobulins co-express the transgenic product. In addition to these observations that apply to both transgenic lines, differences were found between the two lines concerning the quantitative expression of the transgenic IgM, the frequency of cells expressing the transgene and the magnitude of switch. These data are indicative of the complexity of the IgM-transgenic mouse model, in which the phenomenology may depend on the transgene insertional position, on B cell physiology and on immunological mechanisms of recognition, induction and regulation.

Gastric pseudolymphoma with monotypic cytoplasmic immunoglobulin

Two cases of hyperplastic lymphoid lesion of the stomach with cytoplasmic immunoglobulin of monotypic pattern are presented. Both patients were young, and the postgastrectomy course was uneventful for 38 and 76 months, respectively. The lesion had been diagnosed as pseudolymphoma based on the presence of hyperplastic follicles with germinal center and mixed infiltration of plasma cells and mature lymphocytes with no significant cytologic atypia. However, the immunoperoxidase method showed monotypic cytoplasmic immunoglobulin; lambda/IgM in one case and lambda/IgG in the other. The staining pattern of germinal centers was also monotypic in one, but polytypic in the other. These cases suggest the presence of monoclonal but reactive lymphoid hyperplasia, i.e., monoclonal-type pseudolymphoma in the stomach. On the other hand, this type of lesion has to be carefully followed for the possible development of malignant lymphoma.

Effect of anti-gamma 3 antibodies on immunoglobulin isotype expression in lipopolysaccharide-stimulated cultures of mouse spleen cells

To test the hypothesis that gamma 3 is the pivotal isotype for sequential heavy chain switching from mu to each of the gamma isotypes, we have compared the effects of anti-gamma 3 and anti-mu antibodies on the expression of immunoglobulin isotypes in lipopolysaccharide (LPS)-stimulated cultures of mouse spleen cells. IgM-, IgG1-, IgG2b- and IgG2a-containing plasma cells were enumerated by immunofluorescence and secreted immunoglobulins were measured by radioimmunoassay. Although anti-gamma 3 and anti-mu were equally effective in inhibiting the LPS-induced differentiation of IgG3 plasma cells, anti-gamma 3 had no effect on the differentiation of IgM, IgG1, IgG2b, or IgG2a plasma cells. These results support a direct mechanism of heavy chain immunoglobulin switching.

Mitogen-induced switching of immunoglobulin heavy-chain class secretion in chronic B-lymphocytic leukaemia and immunocytoma cell populations

Lymphocytes from peripheral blood, bone marrow, and lymph nodes from six patients with chronic B-lymphoproliferative disease were studied. Two of the patients had a polymorphic immunocytoma with surface membrane immunoglobulin phenotype mu kappa. Four patients had chronic B-lymphocytic leukaemia (CLL) with the phenotypes mu kappa, mu delta kappa, mu lambda, and mu delta lambda, respectively. In no case did the monoclonal cell populations express gamma chains on the surface, and none produced monoclonal immunoglobulin in vivo. The malignant B lymphocytes were cultured in the presence of polyclonal B-cell activators. Immunoglobulin secretion was detected with the protein A plaque assay and with a modification of the reversed haemolysis-in-agar plaque assay. Immunoglobulin secretion was induced in four of the cell populations. In both the immunocytomas and in one of the CLL cell clones the heat-inactivated Staphylococcus aureus strain Cowan I induced secretion of IgG, as well as IgM, associated only with the same light chain as was expressed on the surface of the unstimulated cells. Thus, mitogens can induce immunoglobulin secretion in vitro in malignant B lymphocytes, and Cowan I bacteria also have the ability to induce a switch of immunoglobulin production from IgM to IgG in a fraction of the leukaemic cell populations.

Immunological and histochemical techniques in the study of the malignant lymphomas: a review

Current methods of immunological and enzymatic marker studies used in the investigation of the malignant lymphomas are reviewed and the application of such methods is demonstrated by illustrative examples. The reliability of the various techniques and their relevance to a modern diagnostic laboratory are discussed.

DNA rearrangements in MPC-11 immunoglobulin heavy chain class-switch variants

Immunoglobulin heavy chain class switching has been observed in vitro. In the IgG2b-producing MPC-11 mouse myeloma cell line, IgG2a-producing cells arise at a high frequency. In some cases, switch variants producing normal-sized (Mr 55,000) gamma 2a heavy chains have arisen spontaneously from a mutagen-induced "intermediate" (ICR 9.7.1) that produces an unusually large (Mr 75,000) heavy chain. Other switch variants have been isolated directly from the parent cell line. The expressed and unexpressed gamma 2b genes of MPC-11 can be distinguished in restriction endonuclease digests of total genomic DNA so that DNA rearrangements detected in MPC-11 variants can be directly associated with one or the other of these two genes. We describe here DNA rearrangements occurring on the expressed heavy chain chromosome of several MPC-11 gamma 2a switch variants and on the expressed chromosome of the ICR 9.7.1 intermediate. Our data indicate that all of these variants express the parental heavy chain variable region (VH) gene, supporting previous protein studies. We provide mapping data for the expressed gene of both ICR 9.7.1 and one of the IgG2a-producing variant cell lines (ICR 9.9.2.1) derived from it and discuss the advantages of an in vitro switching system for examining the dynamics of the immunoglobulin heavy chain class switch.

Isotypes of surface immunoglobulin on B lymphocytes from patients with immune deficiency

Peripheral blood lymphocytes from patients with antibody deficiency diseases (primarily agammaglobulinemia) were examined for the presence of B-lymphocyte subsets defined by surface immonoglobulin isotypes. The patients could be classified into one of four groups based upon the presence or absence of particular isotype-defined subsets. Patients with type I agammaglobulinemia lacked cells bearing surface IgG as well as IgD-Igm+-bearing cells. Type II agammaglobulinemia had unusually large numbers of IgG-bearing cells, representing as many as 50% of the peripheral blood B lymphocytes, while other B-cell subsets were present in normal numbers. Type III agammaglobulinemia had apparently normal numbers of all B-cell subsets. Hyper IgM immunodeficiency lacked cells bearing surface IgG, but did have all three iGd/IgM-bearing B-cell subsets. This classification of patients based upon B-cell subsets present in peripheral blood directly correlates with previous functional studies of B cells from these patients. We suggest that abnormal in vitro function of cells from these patients results from abnormal populations of B cells in peripheral blood, which result from the underlying disease.

Linkage of the four gamma subclass heavy chain genes

The genes for the heavy-chain constant regions of the four gamma subclass immunoglobulins were identified in a set of overlapping mouse DNA fragments representing about 100 kilobase pairs (kb) of the mouse genome that was cloned from bacteriophage lambda libraries of BALB/c mouse embryo DNA. R-loop mapping studies show that the genes are located 5'-C gamma 3-34 kb-C gamma 1-21 kb-C gamma 2b-15 kb-C gamma 2a-3' and lie in the same transcriptional orientation. Two DNA segments, one of 19 kb and another of 15 kb, that surround the C gamma 2b and C gamma 2a genes, respectively, show considerable homology and implicate a tandem duplication mechanism in the evolution of this gene cluster.

Diffuse large cell lymphomas (reticulum cell sarcomas, histiocytic lymphomas). Correlation of morphologic features with functional markers

Electron microscopic findings in 15 cases of diffuse large cell lymphoma were correlated with other morphologic features, surface immunotype and cytoplasmic immunoglobulin content. Immunologically, the cases were: B cell, 8; null, 4; T cell, 2; and H cell (true histiocytic), 1. Ultrastructurally, all B cell and three null lymphomas were characterized by an abundance of polyribosomes and segments of rough endoplasmic reticulum. Concentric rough endoplasmic reticulum was observed in 4 cases of B cell lymphoma containing cytoplasmic immunoglobulin and in a null lymphoma. In 1 case of B cell lymphoma, the diastase-sensitive, periodic-acid-Schiff-positive cytoplasm showed evidence of widely dispersed monoparticulate glycogen granules. The two T cell lymphomas contained hyperlobulated or single round nuclei, and abundant smooth to rough endoplasmic reticulum. One null lymphoma appeared to share the ultrastructural features of T cell convoluted nuclei and the cytoplasmic organelles of myeloid precursor cells. The H cell lymphoma had features of monocytic-macrophagic differentiation. The large cell lymphomas, a morphologically and functionally heterogeneous group, were represented predominantly in this series by neoplasms with follicular center cells or early plasma cells.

Two types of somatic recombination are necessary for the generation of complete immunoglobulin heavy-chain genes

At least two types of somatic recombination are necessary for the generation of a complete immunoglobulin gamma 2b gene from germ-line DNA sequences. The first type of recombination consists of the assembly of three separate DNA segments, each encoding a different part of the variable region. The second type of recombination replaces the exons coding for the constant region of the mu chain with those coding for the same region of the gamma 2b chain. The DNA sequencing studies suggest that the two types of recombination operate by different mechanisms.

Rosette-formation with mouse red blood cells in chronic lymphocytic leukemia and leukemic non-Hodgkin's lymphomas

Peripheral blood lymphocytes from 30 patients with chronic lymphocytic leukemia (CLL) and 18 patients with malignant non-Hodgkin's lymphomas in leukemic phase were studied for rosette-formation with neuraminidase-treated mouse erythrocytes. The proportion of rosette-forming cells in CLL was significantly higher (p < 0.001) than in 12 cases of lymphoplasmacytoid malignant lymphoma (LPL). Our results suggest that this test may be a helpful method in the differentiation of CLL from leukemic LPL, which usually can not be distinguished by morphological criteria alone.

Exon shuffling generates an immunoglobulin heavy chain gene

From endonuclease EcoRI partial libraries of DNAs from mouse embryo and MOPC 141, a gamma 2b-producing myeloma, clones were isolated by using a DNA fragment carrying the gamma 2b constant (C) region gene as a hybridization probe. One clone from MOPC 141 contained a heavy chain variable (V) gene and the C gamma 2b gene, as demonstrated by R-loop mapping. The V gene and C gene in this clone were separated by a 3.9-kilobase intron. The characterization of this clone as well as the embryonic clones suggest that at least two recombination events occurred to create the gamma 2b gene in MOPC 141. One of the events is analogous to the V-J joining previously demonstrated in the light chain genes, which brings the major part of the V gene next to a short coding sequence (J). The other event we refer to as "C mu-C gamma 2b switch recombination" because a portion of the intron between the V gene and C gene of the rearranged gamma 2b gene is derived from the 5' flanking sequence of the embryonic C mu gene. A model suggesting how the phenomenon of switch seen in lymphocytes may occur is presented.

Antigen-specific T-helper cells stimulate H-2-compatible and H-2-incompatible B-cell blasts polyclonally

Lipopolysaccharide (LPS)-activated B-cell blasts from C57BL/6J nu/nu spleen cells develop into IgM-secreting clones after stimulation by antigen-specific T-helper cells of C57BL/6J origin. Although induction of help is antigen-dependent, help itself acts polyclonally. 1 of 1--3 B-cell blasts is restimulated in a homologous fashion by LPS, or in a heterologous fashion by sheep erythrocyte (SRC)- or horse erythrocyte (HRC)-activated T-helper cells. The repertoire of activated B-cell blasts reflects the polyclonal nature of activation: approximately 1 in 1,000--3,000 restimulated B-cell blasts is specific for SRC, 1 in 300--1,000 is specific for HRC, and 1 in 100--300 specific for trinitrophenylated SRC (TNP30-SRC). B-cell blasts that are either H-2 compatible or H-2 incompatible with the antigen-activated T-cell help are stimulated polyclonally in similar high frequencies. Thus, neither antigen nor H-2 compatibility are required to stimulate a B-cell blast into the next cell cycle.

Studies of mixed lymphocyte reactions, surface B cell antigens, and intracytoplasmic immunoglobulins in "null cell" acute lymphocytic leukemia

Lymphoblasts from "null cell" acute lymphocytic leukemia (ALL) were analyzed for the pattern of proliferation displayed in a mixed lymphocyte reaction (MLR), the presence of a B cell surface antigen, and for the presence of intracytoplasmic immunoglobulin (ICIg). "Null cell" ALL was defined by cytologic and cytochemical criteria and by the absence of spontaneous rosette formation and surface membrane immunoglobulin in cell suspensions of the malignant lymphocytes. In eleven of fourteen patients the proliferative characteristics of lymphoblasts in the MLR were similar to those observed with normal B enriched lymphocytes. In eleven cases studied, anti-B cell serum reacted with a majority of the lymphoblasts. None of the ten cases examined displayed ICIg in the lymphoblasts. We conclude that the "null" lymphoblast from most cases of ALL is a B cell in an early stage of development.

Cirrhotic hyperglobulinemia: increased rates of immunoglobulin synthesis by circulating lymphoid cells

We have measured immunoglobulin (Ig) synthesis by circulating lymphoid cells of 20 patients with cirrhotic hyperglobulinemia (CH) and 20 age-matched controls. We used specific anti-Ig antisera to precipitate Ig synthesized from [14C] amino acid precursors in 13 controls and employed an electroimmunoassay of the "rocket" type to measure Ig elaborated by cultured cells in 4 patient-control pairs. In addition, we studied 3 patient-control pairs by absorption of elaborated Ig onto an anti-Ig-coated solid phase, bromoacetylcellulose. The synthetic index (SI; the ratio of Ig synthesis by a CH patient and a control) was elevated in every case. Mean SI by coprecipitation was 7.2 +/- 5.4 (mean +/- SD), by rocket" 7.3 +/- 3.0 for IgG and 2.2 +/- 0.8 for IgA, and by immunoabsorption 13.8 +/- 8.4 for IgG. Three cirrhotic nonhyperglobulinemic patient-control pairs showed a mean SI of 1.0 +/- 0.1. CH and control populations showed equal numbers of membrane Ig-positive B lymphocytes by immunofluorescence. We conclude that (1) peripheral blood lymphoid cells are appropriate for study of differences in Ig synthetic capacity among individuals; (2) CH is associated with increased in vitro Ig synthesis; and (3) CH lymphocytes may be an appropriate cell population for the study of control mechanisms in Ig synthesis.

Surface marker studies in chronic lymphocytic leukaemia and non-Hodgkin's lymphoma

Immunological surface marker techniques were applied in a study of 29 cases of chronic lymphocytic leumaemia and 22 of non-Hodgkin's lymphoma. Surface marker characteristics distinguished 2 subtypes of B lymphocytes. Chronic lymphocytic leukaemia was a monoclonal proliferation of B lymphocytes which produced spontaneous rosettes with mouse erythrocytes and had faintly immunofluorescent surface immunoglobulin. The majority of non-Hodgkin's lymphomas also had their origin from B lymphocytes but in contrast, this subtype did not show receptors for mouse erythrocytes and their surface immunoglobulin was brightly staining and demonstrated "capping". The clonal origin of nodular lymphomas could also be demonstrated on frozen sections stained for surface immunoglobulin. Two cases of true histiocytic lymphoma were identified. The current information available on surface marker characteristics of the leukaemias and lymphomas is reviewed.

Separation of T and B lymphocytes from various mouse strains by density gradient electrophoresis

T and B mouse spleen lymphocytes were separated by density gradient electrophoresis on the basis of their surface charge. In all strains examined, the T lymphocytes were found in the high mobility fractions and the B in the low. The T and B cells were separated completely in most fractions, with some overlapping in the middle. Significant differences were found in the electrophoretic distribution profiles between the strains: C57BL/6j, C57BL/10j, (BALB/cXC57BL/6j)F1, and all the following: B6.C-H-2d/cBy (congenic to C57BL/6j), BALB/c, CBA/H/T6j, C57BL/10Sn, and C3H. The C57BL/6j and the (BALB/cXC57BL/6j)F1 cells appear more heterogeneous as far as electrophoretic mobility is concerned. Almost all the other strains give two major peaks. Moreover, the high mobility areas are less populated in the C57BL/6j and the (BALB/cXC57BL/6j)F1 animals than in all the others. The above differences were found consistently when cells prepared by different methods were electrophoresed. It is concluded that the surface charge of lymphocytes may be genetically determined. Possible dependency on the H-2 complex or non-H-2 areas is discussed.

A method for specifically detecting internal immunoglobulin by immunofluorescence

The detection of specifically internal immunoglobulin by staining of fixed preparations of lymphoid cells with appropriate fluorescein-conjugated antisera can be hampered by binding of the conjugates to membrane-bound immunoglobulin. Without preventing staining through membrane-bound immunoglobulin, it is impossible to be sure whether lightly stained cells contain only small amounts of immunoglobulin or wehter the staining is entirely due to the membrane-bound material. Surface immunoglobulin can be stripped from tonsil cells prior to making preparation, and this can be achieved without loss of viable cells. As compared with untreated preparations, pronase-stripped smears contain little non-cellular debris and greatly reduced numbers of small lymphocytes faintly stained by polyvalent anti-human immunoglobulin. The remaining stained cells can be said to specifically contain internal immunoglobulin and are easily scored.

Separation of rat T and B lymphocytes by density gradient electrophoresis

Density gradient electrophoresis has been employed for the preparative separation of T and B lymphocytes from rat spleen and peripheral blood. The high mobility cells were found to be predominantly T lymphocytes, as determined by their response to phytohemagglutinin and the relative absence of immunoglobulin-positive cells. The low mobility cells were predominantly B cells, as determined by the high percentage of immunoglobulin-positive cells and the total lack of response to PHA, an exclusive T cell mitogen. A better separation of peripheral blood T and B lymphocytes was achieved than with spleen T and B cells.

Late appearance of an IgA (kappa) monoclonal protein in a patient with IgG (kappa) multiple myeloma: sharing of idiotypic specificities between the two serum proteins

A patient with an IgG(chi) monoclonal serum protein developed in the course of the disease a second monoclonal spike of the same light chain type and of the IgA class. The latter monoclonal protein progressively increased and eventually exceeded the first IgG(chi) protein. Antigenic analysis of the two myeloma proteins demonstrated that they shared idiotypic determinants. Immunofluorescence studies, carried out with anti gamma and anti alpha reagents tagged with different fluorochromes revealed that the two isotypes were produced by different plasma cells. The data are discussed in the prospect of a possible transitional mechanism from IgG to IgA synthesis within a single B cell clone.

Immunopathology of follicular lymphomas. A model of B-lymphocyte homing

To investigate whether follicular lymphoma has a monoclonal origin, we stained frozen tissue sections from 22 afflicted patients for kappa and lambda light chains with an immunofluorescence technic. F(ab')2 antibody fragments were used to avoid binding by Fc receptors. In 20 cases the lymphoma nodules comprised a monoclonal population of immunoglobulin-producing cells. The nodules were usually surrounded by a normal, polyclonal population of B lymphocytes. Reactive lymphoid follicles were easily differentiated from lymphoma nodules on the basis of clonality. Eight cases contained multiple immunoglobulin heavy chains. All the lymphoma nodules in the same tissue or in multiple tissues in the same patient showed identical light-chain and heavy-chain staining even if different histologic subtypes were identified. Follicular lymphoma is the outgrowth of a single clone of immunoglobulin-bearing cells that retain the tissue-homing characteristics of B lymphocytes.

Immunoglobulin production by lymphocyte hybridomas

We have investigated immunoglobulin production by cloned hybrid cells. gamma2b heavy chains, but not gamma1 or gamma21, exist in two forms, differing in molecular weight, galactose labeling and charge. Hybrid molecules containing gamma2b and gamma1 heavy chains were secreted by hybridoma cells synthesizing Ig molecules of both subclasses. However, cells synthesizing both IgM and IgG chains did not secrete mu-gamma hybrid molecules. We have surveyed many new hybridomas derived from different mouse strains: 10% of those secreting IgM produce a mu chain which is about 5000 daltons larger than normal mu. Two IgM-secreting lines were studied in detail and were found to bear mu but not delta in their membrane. Intra- and extracellular mu differ in molecular size; pentameric IgM-containing molecules of both sizes were observed in the membrane fraction.

Immune status in Crohn's disease. I. Leukocyte and lymphocyte subpopulations in peripheral blood

Proportions and absolute numbers of circulating leukocyte populations and lymphocyte subpopulations (T- and B-cells) were determined in 33 patients with Crohn's disease (group CD), and were compared with those of age- and sex-matched healthy subjects. Group CD comprised 15 patients with newly diagnosed, short-standing, and untreated CD (group CD 1) and 18 patients with long-standing, previously drug treated CD (group CD 2). All CD groups showed a significant absoulte leukocytosis, based on a significant absolute and relative increase of the neutrophils, and, as far as group CD and CD 1 were concerned, also of the absolute number of monocytes. In group CD 1, absolute lymphocyte and relative as well as absolute T-cell numbers were close to normal. In contrast, in group CD 2 absolute as well as relative numbers of lymphocytes and absolute numbers of T-cells were highly significantly reduced, whereas the reduction of the relative T-cell concentration barely reached significance. The proportion of B-cells was significantly above normal in all patient groups, the absolute number in group CD only. Also group CD 1 showed considerably, though statistically insignificantly, higher than normal absolute B-cell numbers. In group CD 1 , there was an inverse correlation between absolute T-cell numbers and disease activity, and between absolute lymphocyte numbers and duration of disease. These data indicate that there is no gross numerical reduction of the carriers of the cell-mediated immunity as a primary predisposing factor for CD, but that a reduction of these cells occurs in the circulation after the disease has started.

The lymphoid system. Its normal architecture and the potential for understanding the system through the study of lymphoproliferative diseases

This article presents a view of lymphoid tissue architecture as defined by the traffic of defined lymphoid cell classes. The compartmentalization of lymphocytes is discussed in reference to specific cell-cell interactions that occur in antigen-driven immune responses. Finally, the distribution of normal and neoplastic lymphocytes in humans is defined and compared with animal model systems.

Inhibition of antibody production in plasmacytoma cells by antigen

Tissue culture-adapted MOPC 315 mouse plasmacytoma cells which secrete monoclonal anti-DNP IgA antibody, were cultured with a variety of DNP-carrier conjugates and the production of IgA measured by pulse labeling with [3H]leucine and by plaque-forming cell assays. DNP-coupled bovine, human and rabbit gamma-globulins (containing 9 to 12 DNP groups per 50 000 mol wt of carrier) inhibited the synthesis and secretion of IgA by 40 to 80%. This inhibition was specific, since unconjugated globulins were ineffective, non-IgA proteins and DNA synthesis remained unaffected, and DNP-globulins had no effect on X5563 cells which do not bind DNP. The degree of suppression of antibody production dependen on the concentration and epitone density of the antigen and on the duration of exposure of cells to it, and was no attributable to absorption of secreted antibody by cell-bound antigen. Comparably substituted DNP conjugates of F(ab')2 and intact globulins were equally inhibitory. The inhibition of antibody synthesis by DNP-BGG was reversible following removal of the antigen. This phenomenon is similar in many respects to the antigen-induced blockade of normal antibody-secreting cells, and provides a valuable model system for analyzing the mechanisms of antigen-mediated cellular inactivation.

[Electrophoretic mobility of lymphocytes in chronic lymphatic leukemia (author's transl)]

Lymphocytes and other blood cells can be separated by means of free flow cell electrophoresis. Immunofluorescence of the separated lymphocytes of four healthy volunteers with antiimmunoglobulins IgD and IgM produced different distribution profiles for each immunoglobulin class, the IgD positive cells migrating faster than the IgM positive ones. Amongst five patients with chronic lymphocytic leukemia four with IgD positive lymphocytes (greater than 80%) showed an identical electrophoretic distribution. The IgM positive lymphocytes (greater than 80%) of the fifth patient migrated much more slowly. The weighted mean of each distribution profile of either the IgD or IgM positive lymphocytes in CLL is similar to that of normal subjects.