A model for the differentiation of B lymphocytes with implications for the biological role of IgD

A Few Key Historical Events in the Antibody Field: The Alacritous Antibody

We have coined the term "alacrity" to describe the extraordinary diversity of B cell activation potentials, even among cells in a single B cell clone responding to a single antigen. The discovery of methodologies for B cell culture in limiting dilution allowed scientists to identify the source of cellular heterogeneity among cells of the immune system. Analyses of individual B cells set the stage for more detailed descriptions of the factors that diversify B cell functions, some of which will be expanded upon by partner articles in this B cell issue.

IgE Production after Four Routes of Injections of Japanese Cedar Pollen Allergen without Adjuvant: Crucial Role of Resident Cells at Intraperitoneal or Intranasal Injection Site in the Production of Specific IgE toward the Allergen

The production of specific IgE antibodies directed toward cedar pollen correlates well with the onset of allergic rhinitis; but the mechanisms of allergen recognition as nonself and Ig class switch to IgE by the immune system are still not fully understood. In the present study, we injected cedar pollen into mice through 4 different routes (intranasal (i.n.), intraperitoneal (i.p.), intravenous (i.v.), and subcutaneous (s.c.)) without adjuvant 1 to 3 times, and determined time-dependent changes in the total and specific serum IgE levels compared with those in the serum levels of other isotype Igs. After an i.p. or i.n. injection of allergen into the mice, they produced a 1.5-to 1.7-fold increase in total IgE, but none in IgG, IgM, or IgA antibodies in their serum, whereas an i.v. or s.c. injection of allergen was inactive as an inducer of total IgE antibodies. Upon a 2nd (s.c.) injection of the allergen into the i.p. or i.n. sensitized mice, a large amount of allergen-specific IgE antibodies was found in the serum. In the case of i.v. or s.c. sensitized mice, however, they produced total, but not specific, IgE antibodies; and a 3rd (s.c.) injection of the allergen resulted in a large amount of specific IgE antibodies in the serum. These results imply that resident cells at the i.p. or i.n. injection site may play a crucial role in the efficient production of total and specific IgE antibodies toward the allergen.

Essential role of macrophages in the initiation of allergic rhinitis in mice sensitized intranasally once with cedar pollen: regulation of class switching of immunoglobulin in B cells by controlling interleukin-4 production in T cells of submandibular lymph nodes

The production of allergen-specific IgE antibodies (Abs) in allergen-sensitized patients or animals has a mutual relationship with the immunologic response leading to allergic rhinitis. We recently reported that, after an intranasal injection of cedar pollen into mice, an interleukin-4 (IL-4)-dependent increase in serum nonspecific IgE Abs was a prerequisite for the production of serum allergen-specific IgE Abs. Here, we explored which lymphoid organs were responsive to the intranasally injected allergen and how IL-4 and IgE Abs were produced in the lymphocytes. Time-dependent changes in the total cell numbers and in in vitro IgE Ab production in various lymphoid organs revealed that the submandibular lymph nodes were the main responsible organ. After treatment with allergen (for IgE production) or allergen and complete Freund's adjuvant (for IgG production), we separated submandibular lymph node cells into macrophage-, lymphocyte-, and granulocyte-rich populations by discontinuous Percoll density-gradient centrifugation. Unexpectedly, bulk cells, but not the lymphocyte- or macrophage-rich populations, produced significant amounts of IL-4, IgE, and IgG; whereas production was restored by addition of Mac-1(+) cells from the macrophage-rich to the lymphocyte-rich fraction. Furthermore, a combination of the lymphocyte-rich population (for IgG [or IgE]) production) and the macrophage-rich population (for IgE [or IgG]) production) produced a large amount of IgE (or IgG). These results indicate that, in the initiation of allergic rhinitis, macrophages in the submandibular lymph nodes are essential not only for IL-4 or immunoglobulin production, but also for class switching of immunoglobulin in lymphocytes.

Function of mucosa-associated lymphoid tissue in antibody formation

Abundant evidence supports the notion that human intestinal plasma cells are largely derived from B cells initially activated in gut-associated lymphoid tissue (GALT). Nevertheless, insufficient knowledge exists about the uptake, processing, and presentation of luminal antigens occurring in GALT to accomplish priming and sustained expansion of mucosal B cells. Also, it is unclear how the germinal center reaction so strikingly promotes class switch to IgA and expression of J chain, although the commensal microbiota appears to contribute to both diversification and memory. B-cell migration from GALT to the intestinal lamina propria is guided by rather well-defined adhesion molecules and chemokines/chemokine receptors, but the cues directing homing to secretory effector sites beyond the gut require better definition. In this respect, the role of human Waldeyer's ring (including adenoids and the palatine tonsils) as a regional mucosa-associated lymphoid tissue must be better defined, although the balance of evidence suggests that it functions as nasopharynx-associated lymphoid tissue (NALT) like the characteristic NALT structures in rodents. Altogether, data suggest a remarkable compartmentalization of the mucosal immune system that must be taken into account in the development of effective local vaccines to protect specifically the airways, small and large intestines, and the female genital tract.

Mucosal B cells: phenotypic characteristics, transcriptional regulation, and homing properties

Mucosal antibody defense depends on a complex cooperation between local B cells and secretory epithelia. Mucosa-associated lymphoid tissue gives rise to B cells with striking J-chain expression that are seeded to secretory effector sites. Such preferential homing constitutes the biological basis for local production of polymeric immunoglobulin A (pIgA) and pentameric IgM with high affinity to the epithelial pIg receptor that readily can export these antibodies to the mucosal surface. This ultimate functional goal of mucosal B-cell differentiation appears to explain why the J chain is also expressed by IgG- and IgD-producing plasma cells (PCs) occurring at secretory tissue sites; these immunocytes may be considered as 'spin-offs' from early effector clones that through class switch are on their way to pIgA production. Abundant evidence supports the notion that intestinal PCs are largely derived from B cells initially activated in gut-associated lymphoid tissue (GALT). Nevertheless, insufficient knowledge exists concerning the relative importance of M cells, major histocompatibility complex class II-expressing epithelial cells, and professional antigen-presenting cells for the uptake, processing, and presentation of luminal antigens in GALT to accomplish the extensive and sustained priming and expansion of mucosal B cells. Likewise, it is unclear how the germinal center reaction in GALT so strikingly can promote class switch to IgA and expression of J chain. Although B-cell migration from GALT to the intestinal lamina propria is guided by rather well-defined adhesion molecules and chemokines/chemokine receptors, the cues directing preferential homing to different segments of the gut require better definition. This is even more so for the molecules involved in homing of mucosal B cells to secretory effector sites beyond the gut, and in this respect, the role of Waldever's ring (including the palatine tonsils and adenoids) as a regional inductive tissue needs further characterization. Data suggest a remarkable compartmentalization of the mucosal immune system that must be taken into account in the development of effective local vaccines to protect specifically the airways, eyes, oral cavity, small and large intestines, and urogenital tract.

The B-cell system of human mucosae and exocrine glands

The mucosae and exocrine glands harbour the largest activated B-cell system of the body, amounting to some 80-90% of all immunoglobulin (Ig)-producing cells. The major product of these immunocytes is polymeric (p)IgA (mainly dimers) with associated J chain. Both pIgA and pentameric IgM contain a binding site for the polymeric Ig receptor (pIgR), or secretory component (SC), which is a requirement for their active external transport through secretory epithelia. The pIgR/SC binding site depends on covalent incorporation of the J chain into the quaternary structure of the polymers when they are produced by the local immunocytes. This important differentiation characteristic appears to be sufficient functional justification for the J chain to be expressed also by most B cells terminating at secretory effector sites with IgD or IgG production; they probably represent a "spin-off" from sequential downstream CH switching on its way to pIgA expression, thus apparently reflecting a maturational stage of effector B-cell clones compatible with homing to these sites. Observations in IgA-deficient individuals suggest that the magnitude of this homing is fairly well maintained even when the differentiation pathway to IgA is blocked. Certain microenvironmental elements such as specific cytokines and dendritic cells appear to be required for induction of IgA synthesis, but it remains virtually unknown why this isotype normally is such a dominating product of local immunocytes and why they have such a high level of J chain expression. Also, despite the recent identification of some important requirements in terms of adhesion molecules (e.g. integrin alpha 4 beta 7 and MAdCAM-1) that explain the "gut-seeking" properties of enterically induced B cells, the origin of regionalized homing of B cells to secretory effector sites outside the gut remains elusive. Moreover, little is known about immune regulation underlying the striking disparity of both the class (IgD, IgM) and subclass (IgA1, IgA2, IgG1, IgG2) production patterns shown by local immunocytes in various regions of the body, although the topical microbiota and other environmental stimuli might be important. Rational design of local vaccines will depend on better knowledge of both inductive and migratory properties of human mucosal B cells.

The normal counterpart of IgD myeloma cells in germinal center displays extensively mutated IgVH gene, Cmu-Cdelta switch, and lambda light chain expression

Human myeloma are incurable hematologic cancers of immunoglobulin-secreting plasma cells in bone marrow. Although malignant plasma cells can be almost eradicated from the patient's bone marrow by chemotherapy, drug-resistant myeloma precursor cells persist in an apparently cryptic compartment. Controversy exists as to whether myeloma precursor cells are hematopoietic stem cells, pre-B cells, germinal center (GC) B cells, circulating memory cells, or plasma blasts. This situation reflects what has been a general problem in cancer research for years: how to compare a tumor with its normal counterpart. Although several studies have demonstrated somatically mutated immunoglobulin variable region genes in multiple myeloma, it is unclear if myeloma cells are derived from GCs or post-GC memory B cells. Immunoglobulin (Ig)D-secreting myeloma have two unique immunoglobulin features, including a biased lambda light chain expression and a Cmu-Cdelta isotype switch. Using surface markers, we have previously isolated a population of surface IgM-IgD+CD38+ GC B cells that carry the most impressive somatic mutation in their IgV genes. Here we show that this population of GC B cells displays the two molecular features of IgD-secreting myeloma cells: a biased lambda light chain expression and a C&mu-Cdelta isotype switch. The demonstration of these peculiar GC B cells to differentiate into IgD-secreting plasma cells but not memory B cells both in vivo and in vitro suggests that IgD-secreting plasma and myeloma cells are derived from GCs.

Terminally differentiated human intestinal B cells. IgA and IgG subclass-producing immunocytes in the distal ileum, including Peyer's patches, compared with lymph nodes and palatine tonsils

The relative distribution of IgA and IgG subclass-producing immunocytes was examined by two-colour immunohistochemistry in normal human distal ileum including Peyer's patches (PP), regional mesenteric lymph nodes (MLN), and peripheral lymph nodes. IgA2 cells predominated slightly over IgA1 cells in the PP dome area. There was a decreasing median proportion of IgA2 cells in the order of PP (52%), distant ileal lamina propria (40%), MLN (32%), and peripheral lymph nodes (11%). The reverse was true for IgA1 cells in independent enumerations. These results support the notion that PP-derived B cells after stimulation are seeded mainly to the lamina propria of the distal gut, but that there is a substantial retention and terminal differentiation of this migrating population in regional MLN. The median subclass proportions of IgG-producing cells in the PP dome area were in independent determinations 68% IgG1, 23% IgG2, 8% IgG3, and 9% IgG4. This distribution was fairly similar to that seen in other tissue categories, except for a trend towards increased IgG1 and reduced IgG2 proportions in peripheral lymph nodes and reduced IgG1 along with increased IgG3 in normal palatine tonsils. The data suggested an association between the expression of IgG2 (and possibly IgG4) and IgA2 in intestinal mucosal immune responses.

Immunobarriers of the mucosa of the upper respiratory and digestive pathways

The mucosa that lines the upper respiratory and digestive pathways is protected by a secretory immune system which is under complex and only partly understood immunoregulatory control. B cells of relatively immature memory clones with a potential for J-chain expression, are initially stimulated in mucosa-associated lymphoid tissue (probably including the tonsils) and migrate thereafter through lymph and blood to glandular sites where they are subjected to terminal differentiation and become immunoglobulin (Ig)-producing immunocytes. Most locally produced Ig is normally dimeric IgA which is selectively transported through the serous type of glandular cells by means of an epithelial receptor protein called the secretory component (SC). IgM is also subjected to SC-mediated transport. In patients with selective IgA deficiency, secretory IgA is lacking, but may be satisfactorily replaced by protective secretory IgM. In other IgA-deficient patients, however, immunoregulatory compensation gives rise to a large number of IgD-producing cells in respiratory mucosa. IgD cannot act as a secretory antibody and these patients are prone to have recurrent infections. These observations show that there are large individual variations in the secretory immune system.

The presence of immunoglobulin D in endocrine disorders and diseases of immunoregulation, including the acquired immunodeficiency syndrome

Immunoglobulin D (IgD) was determined by double diffusion in the serum from 26 patients with endocrine disorders and diseases of immune imbalance along with controls. IgD was detected in the serum of nine patients that included two with primary parathyroidism, one with insulin-resistant diabetes, four with immunodeficiencies, and two with Hodgkin's disease. IgD was absent in the serum of seven patients with the same diagnoses after treatment. IgD was present in the serum of the majority of acquired immune deficiency syndrome patients (in eight of ten cases). The presence of IgD in the serum of these patients suggests that it plays a role in receptor-mediated events.

Quantitative aspects of IgD and secretory immunoglobulins in middle ear effusions

Levels of the true secretory immunoglobulins, secretory IgA (SIgA) and secretory IgM (SIgM) were determined in middle ear effusions (MEEs) from children with secretory otitis media (SOM) and correlated to the MEE levels of IgD. Double sandwich enzyme-linked immunosorbent assays (ELISA) were used for the quantitative determinations. The levels of SIgM were expressed arbitrarily in units using a nasopharyngeal secretion pool as a standard. The quantitative data substantiated a local synthesis of IgD to the middle ear cavity. In 8/45 MEEs more than 600 mg/l of IgD could be calculated and between 70% and 98% could be considered to be locally produced. A statistically significant correlation was observed between SIgA and SIgM. The results are discussed in the context of the possibility that IgD plasma cells located in the middle ear cavity may primarily originate from the nasopharyngeal tonsils.

Correlation of immunophenotype to morphology in unfavourable non-Hodgkin lymphoma

The relationship between immunological markers and histology according to the Kiel classification was studied in 40 adult non-Hodgkin lymphoma patients of Rappaport unfavourable histology. The membrane-associated and cytoplasmic Ig as well as receptors for sheep erythrocytes, Fc gamma and C3d receptors were analyzed on cryostate sections and in suspension. In some cases, a more precise immunophenotype was achieved by the use of monoclonal antibodies detecting different T and B cell antigens. Eighty-eight per cent of the lymphomas had B-cell, five per cent T cell and 7 per cent non-B/non-T cell phenotypes. All CBCC and CC lymphomas expressed monotypic Ig, but only 66 per cent of the CB lymphomas. Thus, morphology alone did not consistently predict immunophenotype in large-cell lymphomas. A simultaneous expression of multiple heavy chains and cytoplasmic Ig was found in some lymphomas, suggesting an intratumoral differentiation. The nodular or irregular tissue distribution patterns for Ig and C3d receptors found in histologically diffuse follicle derived lymphomas also suggest intratumoral variations in the marker expression, probably related to differentiation. The results suggest that lymphoma immunophenotype is important in obtaining a definite diagnosis in large-cell lymphomas and that it may lead to a better understanding of the differentiation of lymphomas of low-grade malignancy.

B-lymphoproliferative disorders: a proposed unified pathogenetic pathway

The clinical features of lymphoproliferative diseases associated with paraproteinemia are briefly reviewed and correlated with current immunologic concepts in an effort to clarify the pathophysiology of B-lymphocyte disorders. B-lymphocyte maturation proceeds in a predictable manner from the Pre-B cell to the formation of idiotype specific plasma cells and memory B-lymphocytes. The immunoglobulin isotype produced by the mature plasma cell is determined by a site specific process of gene switching which proceeds from mu to alpha production. Lymphoproliferative diseases are the result of disordered B cell maturation and their clinical features can be explained by identifying the locus of the maturational defect.

Heterogeneity of B-cells

Two rat monoclonal antibodies, NIM-R2 and NIM-R3, were prepared that only recognize B-cells in murine secondary lymphoid tissues. Both showed differential reactivity in that they reacted most strongly with nonoverlapping populations of B-cells. They also reacted differentially with some cells of the primary lymphoid tissue, recognizing 90-95% of bone marrow cells, again in a nonoverlapping manner and with NIM-R2 accounting for twice as many cells as NIM-R3. The antibody NIM-R2, but not NIM-R3, also recognized thymocytes and red blood cells. The determinant recognized by NIM-R2 is of interest because it fluctuates at four defined stages of B-cell development: pre-B to immature B, activation of mature B, differentiation of memory cells, and differentiation of antibody-secreting cells. Particularly noteworthy was the differential reactivity of NIM-R2 with virgin and memory B-cells. Those cells that stained strongly with the antibody gave excellent primary responses, but were unable to transfer secondary responses, whereas weakly stained B-cells transferred memory, but could not generate primary antibody responses in vitro. Thus NIM-R2 recognized a cell-surface determinant that presumably decreases in density as primary B-cells differentiate into memory B-cells. A survey of sIg, I-A, Fc receptors, and major glycoproteins of B-cells from spleen, Peyer's patches, mesenteric lymph nodes, and peripheral lymph nodes failed to reveal any major differences between the cells from these different lymphoid organs.

Cell lineage in lymphoproliferative disease

Surface marker techniques have made a major contribution to the understanding and classification of lymphoproliferative disorders by permitting the determination of B- and T-cell lineage. The frequent malignant proliferations of B lymphocytes are identified by the presence of surface immunoglobulin of a single light-chain type; Ia-like (HLA-DR) antigen is present as well. While most T-cell proliferations exhibit the classic receptor for sheep erythrocytes, commercially available monoclonal antisera permit the secure identification of T cells and their subclassification into inducer-helper and cytotoxic-suppressor subsets. Surface markers have also allowed the separation of a fraction of patients with acute lymphocytic leukemia whose cells have T-lymphocyte markers from the majority whose cells show subtle evidence of early B-cell differentiation.

Rearrangements and deletions of immunoglobulin heavy chain genes in the double-producing B cell lymphoma I.29

The B cell lymphoma I.29 consists of a mixture of cells expressing membrane-bound immunoglobulin M (IgM) (lambda) and IgA (lambda) of identical idiotypes. Whereas most of the cells express either IgM or IgA alone, 1 to 5% of the cells in this tumor express IgM and IgA simultaneously within the cytoplasm and on the cell membrane (R. Sitia et al., J. Immunol. 127:1388-1394, 1981; R. Sitia, unpublished data). When IgM+ cells are purified from the lymphoma and passaged in mice or cultured, a portion of the cells convert to IgA+. These properties suggest that some cells of the I.29 lymphoma may undergo immunoglobulin heavy chain switching, although it is also possible that the mixed population was derived by a prior switching event in a clone of cells. We performed Southern blotting experiments on genomic DNAs isolated from populations of I.29 cells containing variable proportions of IgM+ and IgA+ cells and on a number of cell lines derived from the lymphoma. The results were consistent with the deletion model for heavy chain switching, as the IgM+ cells contained rearranged mu genes and alpha genes in the germ line configuration on both the expressed and nonexpressed heavy chain chromosomes, whereas the IgA+ cells had deleted both mu genes and contained one rearranged and one germ line alpha gene. In addition, segments of DNA located within the intervening sequence 5' to the mu gene, near the site of switch recombination, were deleted from both the expressed and the nonexpressed chromosomes. Although mu genes were deleted from both chromosomes in the IgA+ cells, the sites of DNA recombination differed on the two chromosomes. On the expressed chromosome, Smu sequences were recombined with S alpha sequences, whereas on the nonexpressed chromosome, Smu sequences were recombined with S gamma 3 sequences.

Relationship between reduced B cell susceptibility to IgM antibodies and reduced IgD-bearing B cells in patients with systemic lupus erythematosus

Peripheral blood lymphocytes from 14 patients with systemic lupus erythematosus, 5 patients with rheumatoid arthritis, and 10 normal subjects were cultured for 7 days with or without anti-IgM or anti-IgD antibodies, and IgG- and IgM-secreting cells were assayed by reverse hemolytic plaque assay. Surface immunoglobulin (Ig) isotypes on peripheral blood B cells were also examined by a direct anti-Ig rosetting reaction. In normal subjects and rheumatoid arthritis patients, the spontaneous development of IgG- and IgM-secreting cells was markedly suppressed by anti-IgM or anti-IgD antibodies. Over 50% of peripheral blood B cells were IgD- and IgM-bearing cells in normal subjects and in most patients with rheumatoid arthritis. In lupus patients, however, the suppression of IgG and IgM production by anti-IgM or anti-IgD antibodies was remarkably reduced, especially in the active stage. Furthermore, the percentage of IgD-bearing cells in peripheral blood B cells was remarkably reduced, especially in patients with active disease. There was a good correlation between reduced susceptibility of B cells to anti-IgM antibody-mediated suppression and reduced percentage of IgD-bearing cells in lupus patients.

Biosynthesis and structure of membrane and secretory immunoglobulins

Almost all of the body's extracellular immunoglobulin (Ig) is derived from Ig-secreting plasma cells of lymphoid tissues. The secreted material is a heterogeneous mixture of different classes and specificities. Lymphoid tissues also contain a large number of essentially non-secretory cells--B lymphocytes--which bear Ig firmly associated with their plasma membranes. Ig molecules thus exist in two functionally different forms, as membrane-bound antigen receptors on the surface of B lymphocytes on the one hand, and as humoral secreted Ig antibodies on the other. On B cells, membrane-bound heavy chains have an apparent mol. wt. slightly larger than that of secreted heavy chains from plasma cells. Membrane-bound but not secreted heavy chains bind detergents, thus suggesting the presence of a hydrophobic region in membrane-bound heavy chains, which is absent in secreted heavy chains. Most investigations have dealt with immunoglobulin M. The two types of IgM heavy chains differ at their carboxy termini. Recent investigations at the nucleic acid level demonstrate that membrane-associated mu chains contain a 41-residue hydrophobic tail adjacent to the last constant domain, whereas secretory mu chains contain a 20-residue hydrophilic tail. At the present time, evidence is accumulating that all membrane-bound Ig heavy chain classes may contain similar hydrophobic structures necessary for anchorage of the molecules into the lipid bilayer.

Rearrangements and deletions of immunoglobulin heavy chain genes in the double-producing B cell lymphoma I.29

The B cell lymphoma I.29 consists of a mixture of cells expressing membrane-bound immunoglobulin M (IgM) (lambda) and IgA (lambda) of identical idiotypes. Whereas most of the cells express either IgM or IgA alone, 1 to 5% of the cells in this tumor express IgM and IgA simultaneously within the cytoplasm and on the cell membrane (R. Sitia et al., J. Immunol. 127:1388-1394, 1981; R. Sitia, unpublished data). When IgM+ cells are purified from the lymphoma and passaged in mice or cultured, a portion of the cells convert to IgA+. These properties suggest that some cells of the I.29 lymphoma may undergo immunoglobulin heavy chain switching, although it is also possible that the mixed population was derived by a prior switching event in a clone of cells. We performed Southern blotting experiments on genomic DNAs isolated from populations of I.29 cells containing variable proportions of IgM+ and IgA+ cells and on a number of cell lines derived from the lymphoma. The results were consistent with the deletion model for heavy chain switching, as the IgM+ cells contained rearranged mu genes and alpha genes in the germ line configuration on both the expressed and nonexpressed heavy chain chromosomes, whereas the IgA+ cells had deleted both mu genes and contained one rearranged and one germ line alpha gene. In addition, segments of DNA located within the intervening sequence 5' to the mu gene, near the site of switch recombination, were deleted from both the expressed and the nonexpressed chromosomes. Although mu genes were deleted from both chromosomes in the IgA+ cells, the sites of DNA recombination differed on the two chromosomes. On the expressed chromosome, Smu sequences were recombined with S alpha sequences, whereas on the nonexpressed chromosome, Smu sequences were recombined with S gamma 3 sequences.

Immunoglobulins G, M, A, D and E in Behcet's syndrome

Serum IgG, IgM, IgA, IgD and IgE concentrations were examined in 26 patients with Behcet's syndrome, 70 patients with recurrent aphthous stomatitis and 56 healthy controls. IgA concentrations, but not IgG, IgM, IgD or IgE, were significantly raised in Behcet's syndrome compared with controls. Serum IgD and IgE concentrations but not IgA, IgG, or IgM were significantly greater in recurrent aphthous stomatitis than in controls.

Human lymphocyte production of corticotropin and endorphin-like substances: association with leukocyte interferon

Human leukocyte interferon (hIFN-alpha) preparations contain immunologically and biologically recognizable endorphin and corticotropin-like (ACTH-like) activities. The ACTH bioactivity was demonstrable only after pepsin or acid treatment. Highly purified hIFN-alpha was composed of two molecular species of interferon (18,500 and 23,000 daltons). Endorphin activity was associated with both of these molecules. Pepsin treatment of the 23,000-dalton but not the 18,500-dalton hIFN-alpha generated ACTH activity. In acid, the 23,000-dalton hIFN-alpha broke down into the 18,500-dalton form and ACTH (4500 daltons). The ACTH derived from hIFN-alpha by pepsin digestion comigrated with a purified ACTH standard in NaDodSO4/polyacrylamide gel electrophoresis. hIFN-alpha-producing lymphocytes showed positive immunofluorescence after staining with highly specific antisera to ACTH alpha-(1-13) and gamma-endorphin. Essentially 100% of the human peripheral lymphocytes were capable of producing both ACTH and gamma-endorphin-related substances, presumably associated with hIFN-alpha. These results strongly suggest a circuit between the immune and neuroendocrine systems which involves neuroendocrine hormone-like substances, some of which are associated with hIFN-alpha

Rabbit antisera with specificity for isolated mouse T-lymphocyte receptors

Rabbit antibodies obtained after immunization of mouse immunoglobulin (MIg)-tolerant rabbits with B6 anti-CBA IgG and having specificity for B6 anti-CBA IgG and T-cell receptors (antiserum 5936) were used to isolate 5936-reactive molecules from B6 anti-CBA mixed lymphocyte culture supernatants. Such 5936-reactive molecules were produced by the B6 T cells, and they did not react with rabbit anti-MIg antisera. They had a mol. wt of 50,000-75,000, and were single-chain polypeptides that did not react with concanavalin A (Con A)--Sepharose. These molecules were in turn injected into rabbits, and the antisera thus obtained had the following characteristics: (1) they reacted against B6 anti-CBA T-cell receptor material but not against B6 anti-CBA IgG; (2) they reacted with about 35% of B6 (H-2b, Ig-1b) anti-CBA T cells, 25% of B6 Con A blasts and 0-10% of normal B6 T cells but not with B6 lipopolysaccharide (LPS) blasts, C3H.B10 (H-2b, Ig-1j) anti-CBA or CBA anti-B6 T cells, CBA Con A blasts or normal CBA T cells; and (3) they reacted with the same 50,000-75,000 mol. wt, T-cell-derived molecules as did antiserum 5936. The implications of these findings are discussed in relation to the nature of T-cell receptors.

Quantitation of complement C3b and C3d surface receptors on neoplastic IgM positive B lymphocytes

C3b and C3d complement receptors on the surface of mononuclear cells from blood, lymph nodes, and spleens were investigated in twenty-nine CLL patients and in eight patients with non-Hodgkin malignant lymphoma. Compared with a normal material, especially the lymphoid tissues but also the blood of the patients contained a high number of C3d receptor positive lymphocytes with a strong expression of C3d receptors per cell. The majority of the cells with high C3d receptor expression also had SmIgM. The number of C3b receptor positive cells was decreased in the patients but the C3b receptor expression per cell was normal.

Expression of cell surface markers after human B lymphocyte activation

The fate of two recently described human B lymphocyte-specific antigens (B1 and B2) was studied after B-cell activation in vivo and in vitro. Whereas both B1 and B2 were present on virtually all B cells from normal lymph nodes, B2 was absent from approximately 50% of B cells from hyperplastic lymph nodes. When B cells from spleen, tonsil, or peripheral blood were stimulated in vitro with pokeweed mitogen, activated cells were found to lose B2 (days 4-5) and subsequently B1 (days 6-7). Temporally, B2 loss was accompanied by loss of surface IgD, expression of T10, and the development of intracytoplasmic IgM; B1 loss was correlated with the acquisition of surface IgG and the appearance of intracytoplasmic IgG. Peripheral blood B cells, on which B2 is normally only weakly expressed (B1++++B2+) in contrast to B cells from secondary lymphoid organs (B1++++B2++), exhibited a transitory increase in B2 expression to the B1++++B2++ phenotype prior to B2 disappearance during activation. Taken together with other findings, this observation suggests that peripheral blood may contain a relatively immature subpopulation of B cells.

Mouse immunoglobulin D: messenger RNA and genomic DNA sequences

The molecular structure of a mouse immunoglobulin D from a plasmacytoma tumor and that of the normal mouse gene coding for immunoglobulin D are presented. The DNA sequence results indicate an unusual structure for the tumor delta chain in two respects: (i) Only two constant (C) region domains, termed C delta 1 and C delta 3 by homology considerations, are found; the two domains are separated by an unusual hinge region C delta H that lacks cysteine residues and thus cannot provide the covalent cross-links between heavy chains typically seen in immunoglobulins. The two domains and hinge are all coded on separate exons. (ii) At the carboxyl end of the delta chain there is a stretch of 26 amino acids that is coded from an exon located 2750 to 4600 base pairs downstream from the rest of the gene. Analogy with immunoglobulin M suggests that this distally coded segment C delta DC may have a membrane-binding function; however, it is only moderately hydrophobic. A fifth potential exon (C delta AC), located adjacent to the 3' (carboxyl) end of C delta 3, could code for a stretch of 49 amino acids. The tumor's expression of the delta gene may be aberrant, but the simplest interpretation would be that this tumor expresses one of the several biologically significant forms of the delta chain.

Different species of messenger RNA encode receptor and secretory IgM mu chains differing at their carboxy termini

Biosynthetic studies in the presence of an inhibitor of glycosylation indicate that individual human lymphoma-derived cell lines can synthesize both membrne receptor and presumptive secretory forms of IgM mu chains. The receptor form has a larger polypeptide chain than the secretory form and possesses a different C-terminus, but similar N-terminus, consistent with the presence of a C-terminal hydrophobic "tail" for integral membrane binding. Messenger RNA isolated from these cells directs the synthesis of both forms of mu chains in a wheat germ translation system, indicating the presence of independent mRNAs for each form. It is proposed that the synthetic pathways for receptor and secretory IgM diverge at the post-transcriptional level, possibly by differential RNA splicing to give mRNA molecules with or without a translatable "tail" segment.

Rearrangement of immunoglobulin heavy chain genes during B-lymphocyte development as revealed by studies of mouse plasmacytoma cells

We have used Southern's blotting technique to determine the extent to which the genes encoding the constant (C) regions of mu, alpha, gamma(1), and gamma(2b) immunoglobulin heavy (H) chains are altered in number and context from their germline (embryo) state in a series of 14 plasmacytomas expressing various H chain classes. In the three mu chain-producing plasmacytomas studied there was no evidence of rearrangement of C(H) genes other than C(mu). In contrast, rearrangement and deletion of nonexpressed C(H) genes was frequent in plasmacytomas that produce gamma or alpha chains. The observed pattern of deletions is consistent with the idea that the ontogenetic switch in H chain class requires C(H) gene deletion. Frequently, though not always, such deletions as well as other types of rearrangement occur in both allelic loci. Particularly noteworthy are three gamma(2a)-expressing tumors in which C(alpha) gene rearrangement is evident in both alleles. We incorporate these observations into a probabilistic model of B cell development: in the first phase, deletions may occur between the C(mu) gene and the variable (V(H)) gene array, which result in the formation of a productive fused V(H)-C(mu) gene. The cell may then enter a second phase, which allows deletions within the C(H) gene arrays of both homologous chromosomes. Some deletions juxtapose the expressed V(H) gene with a second C(H) gene and result in a H chain class switch; others delete or alter the context of C(H) genes without changing the phenotype of the cell. We predict that switching can be both a single-step and a multi-step process, and that in the latter case those rearrangements that do not result in a switch may be physiologically significant in that they may limit the options of further switching.

Serum IgD concentrations in normal infants, children, and adults and in patients with elevated IgE

Earlier studies of serum immunoglobulin D concentrations were hampered by the insensitivity of single radial diffusion, since most normal individuals have IgD concentrations in a range below or near the limit of sensitivity of that method. Using a sensitive double-antibody radioimmunoassay, we measured serum IgD in normal individuals from 28 weeks' gestational age to 70 years of age and in several groups of diseased individuals, many of whom had elevated serum IgE concentrations. The group mean serum IgD concentration in children one to 20 years of age was 13.65 IU/ml. Premature and term neonates had levels that did not differ significantly from each other (0.22 and 0.14 IU/ml, respectively), but that were far lower than serum IgD concentrations in normal children one to 20 years of age (P = less than 10-9), indicating that mature levels of IgD are achieved sometime during the first year of life. Normal adults aged 21 to 70 years, atopic children with or without eczema, children with serum IgE values greater than 2,000 IU/ml, and children with cystic fibrosis all had group mean IgD concentrations that did not differ significantly from that of normal children. In contrast, 20 patients with the hyper IgE syndrome had a mean serum IgD concentration of 94.22 IU/ml, significantly higher than the normal or any other group mean (P = less than 10-5).

Innunocytological studies on the constituent cells of the secondary nodules in human tonsils

The rate of presence of surface immunoglobulins (sIg) and incidence of the surface receptors (SRBC-receptor, Fc-receptor and C3 receptor) were examined on the constituent cells of secondary nodules enucleated from human tonsils and foated in suspension. As most of the rosette-forming cells for SRBC-receptor were judged to belong to small round cells, the germinal center was considered to be a "non-T-cell region." The coronal B-lymphocytes and small germinal center cells were fairly matured B-cells because both bore sIg (100%), Fc receptor (25%) and C3 receptor (90-80%), while the former cells were thought to be more matured on the basis of their possession of surface delta-chain. As the large germinal center cells bore sIg (50%) and carried Fc receptor (25%) and C3 receptor (50%), they seemed to be the major immature cells among the cell constituents of the secondary nodules. Moreover, it is presumed that the majority of the large germinal center cells are able to differentiate into coronal B-lymphocytes, probably memory cells, and a minor population of them into cIg-containing cells.