Distribution of immunoglobulin-containing cells in human bone marrow and lymphoid tissues

Know your enemy or find your friend?-Induction of IgA at mucosal surfaces

Most antibodies produced in the body are of the IgA class. The dominant cell population producing them are plasma cells within the lamina propria of the gastrointestinal tract, but many IgA-producing cells are also found in the airways, within mammary tissues, the urogenital tract and inside the bone marrow. Most IgA antibodies are transported into the lumen by epithelial cells as part of the mucosal secretions, but they are also present in serum and other body fluids. A large part of the commensal microbiota in the gut is covered with IgA antibodies, and it has been demonstrated that this plays a role in maintaining a healthy balance between the host and the bacteria. However, IgA antibodies also play important roles in neutralizing pathogens in the gastrointestinal tract and the upper airways. The distinction between the two roles of IgA - protective and balance-maintaining - not only has implications on function but also on how the production is regulated. Here, we discuss these issues with a special focus on gut and airways.

SARS-CoV-2 infection induces long-lived bone marrow plasma cells in humans

Long-lived bone marrow plasma cells (BMPCs) are a persistent and essential source of protective antibodies^1-7. Individuals who have recovered from COVID-19 have a substantially lower risk of reinfection with SARS-CoV-2^8-10. Nonetheless, it has been reported that levels of anti-SARS-CoV-2 serum antibodies decrease rapidly in the first few months after infection, raising concerns that long-lived BMPCs may not be generated and humoral immunity against SARS-CoV-2 may be short-lived^11-13. Here we show that in convalescent individuals who had experienced mild SARS-CoV-2 infections (n = 77), levels of serum anti-SARS-CoV-2 spike protein (S) antibodies declined rapidly in the first 4 months after infection and then more gradually over the following 7 months, remaining detectable at least 11 months after infection. Anti-S antibody titres correlated with the frequency of S-specific plasma cells in bone marrow aspirates from 18 individuals who had recovered from COVID-19 at 7 to 8 months after infection. S-specific BMPCs were not detected in aspirates from 11 healthy individuals with no history of SARS-CoV-2 infection. We show that S-binding BMPCs are quiescent, which suggests that they are part of a stable compartment. Consistently, circulating resting memory B cells directed against SARS-CoV-2 S were detected in the convalescent individuals. Overall, our results indicate that mild infection with SARS-CoV-2 induces robust antigen-specific, long-lived humoral immune memory in humans.

SARS-CoV-2 infection induces long-lived bone marrow plasma cells in humans

Infection or vaccination induces a population of long-lived bone marrow plasma cells (BMPCs) that are a persistent and essential source of protective antibodies1-5. Whether this population is induced in patients infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is unknown. Recent reports have suggested that SARS-CoV-2 convalescent patients experience a rapid decay in their antigen-specific serum antibodies, raising concerns that humoral immunity against this virus may be short-lived6-8. Here we show that in patients who experienced mild infections (n=73), serum anti-SARS-CoV-2 spike (S) antibodies indeed decline rapidly in the first 3 to 4 months after infection. However, this is followed by a more stable phase between 4- and 8-months after infection with a slower serum anti-S antibody decay rate. The level of serum antibodies correlated with the frequency of S-specific long-lived BMPCs obtained from 18 SARS-CoV-2 convalescent patients 7 to 8 months after infection. S-specific BMPCs were not detected in aspirates from 11 healthy subjects with no history of SARS-CoV-2 infection. Comparable frequencies of BMPCs specific to contemporary influenza virus antigens or tetanus and diphtheria vaccine antigens were present in aspirates in both groups. Circulating memory B cells (MBCs) directed against the S protein were detected in the SARS-CoV-2 convalescent patients but not in uninfected controls, whereas both groups had MBCs against influenza virus hemagglutinin. Overall, we show that robust antigen specific long-lived BMPCs and MBCs are induced after mild SARS-CoV-2 infection of humans.

Influenza vaccine-induced human bone marrow plasma cells decline within a year after vaccination

A universal vaccine against influenza would ideally generate protective immune responses that are not only broadly reactive against multiple influenza strains but also long-lasting. Because long-term serum antibody levels are maintained by bone marrow plasma cells (BMPCs), we investigated the production and maintenance of these cells after influenza vaccination. We found increased numbers of influenza-specific BMPCs 4 weeks after immunization with the seasonal inactivated influenza vaccine, but numbers returned to near their prevaccination levels after 1 year. This decline was driven by the loss of BMPCs induced by the vaccine, whereas preexisting BMPCs were maintained. Our results suggest that most BMPCs generated by influenza vaccination in adults are short-lived. Designing strategies to enhance their persistence will be a key challenge for the next generation of influenza vaccines.

The human intestinal B-cell response

The intestinal immune system is chronically challenged by a huge plethora of antigens derived from the lumen. B-cell responses in organized gut-associated lymphoid tissues and regional lymph nodes that are driven chronically by gut antigens generate the largest population of antibody-producing cells in the body: the gut lamina propria plasma cells. Although animal studies have provided insights into mechanisms that underpin this dynamic process, some very fundamental differences in this system appear to exist between species. Importantly, this prevents extrapolation from mice to humans to inform translational research questions. Therefore, in this review we will describe the structures and mechanisms involved in the propagation, dissemination, and regulation of this immense plasma cell population in man. Uniquely, we will seek our evidence exclusively from studies of human cells and tissues.

Application of an enzyme-labeled antigen method for visualizing plasma cells producing antibodies against Strep A, a carbohydrate antigen of Streptococcus pyogenes, in recurrent tonsillitis

Streptococcus pyogenes is the main causative pathogen of recurrent tonsillitis. Histologically, lesions of recurrent tonsillitis contain numerous plasma cells. Strep A is an antigenic carbohydrate molecule on the cell wall of S. pyogenes. As expected, plasma cells in subjects with recurrent tonsillitis secrete antibodies against Strep A. The enzyme‐labeled antigen method is a novel histochemical technique that visualizes specific antibody‐producing cells in tissue sections by employing a biotin‐labeled antigen as a probe. The purpose of the present study was to visualize plasma cells producing antibodies reactive with Strep A in recurrent tonsillitis. Firstly, the lymph nodes of rats immunized with boiled S. pyogenes were paraformaldehyde‐fixed and specific plasma cells localized in frozen sections with biotinylated Strep A. Secondly, an enzyme‐labeled antigen method was used on human tonsil surgically removed from 12 patients with recurrent tonsillitis. S. pyogenes genomes were PCR‐detected in all 12 specimens. The emm genotypes belonged to emm12 in nine specimens and emm1 in three. Plasma cells producing anti‐Strep A antibodies were demonstrated in prefixed frozen sections of rat lymph nodes, 8/12 human specimens from patients with recurrent tonsillitis but not in two control tonsils. In human tonsils, Strep A‐reactive plasma cells were observed within the reticular squamous mucosa and just below the mucosa, and the specific antibodies belonged to either IgA or IgG classes. Our technique is effective in visualizing immunocytes producing specific antibodies against the bacterial carbohydrate antigen, and is thus a novel histochemical tool for analyzing immune reactions in infectious disorders.

Mathematical modeling provides kinetic details of the human immune response to vaccination

With major advances in experimental techniques to track antigen-specific immune responses many basic questions on the kinetics of virus-specific immunity in humans remain unanswered. To gain insights into kinetics of T and B cell responses in human volunteers we combined mathematical models and experimental data from recent studies employing vaccines against yellow fever and smallpox. Yellow fever virus-specific CD8 T cell population expanded slowly with the average doubling time of 2 days peaking 2.5 weeks post immunization. Interestingly, we found that the peak of the yellow fever-specific CD8 T cell response was determined by the rate of T cell proliferation and not by the precursor frequency of antigen-specific cells as has been suggested in several studies in mice. We also found that while the frequency of virus-specific T cells increased slowly, the slow increase could still accurately explain clearance of yellow fever virus in the blood. Our additional mathematical model described well the kinetics of virus-specific antibody-secreting cell and antibody response to vaccinia virus in vaccinated individuals suggesting that most of antibodies in 3 months post immunization were derived from the population of circulating antibody-secreting cells. Taken together, our analysis provided novel insights into mechanisms by which live vaccines induce immunity to viral infections and highlighted challenges of applying methods of mathematical modeling to the current, state-of-the-art yet limited immunological data.

IgG4-Related Fibrotic Diseases from an Immunological Perspective: Regulators out of Control?

Patients with autoimmune pancreatitis have a striking polyclonal elevation of total IgG4 in serum. This observation has been confirmed and extended to other fibrotic conditions (that are therefore called IgG4-related disease) but as yet remains unexplained. The affected tissue contains many IgG4-producing plasma cells embedded in a fibrotic matrix originating from activated mesenchymal (stellate) cells. We propose that the process results from an unusual interaction between two regulatory systems: the regulatory arm of the immune system (including Bregs) and the tissue repair regulatory components orchestrated by the activated stellate cell. This interaction results in ongoing mutual activation, generating TGFbeta, IL10, and vitamin D. This environment suppresses most immune reactions but stimulates the development of IgG4-producing plasma cells.

Non-secretory or low-secretory myeloma with intracellular kappa chains. Report of six cases and review of the literature

This report concerns six cases of multiple myeloma characterized by either no demonstrable monoclonal immunoglobulin in plasma or urine or by trace amounts (less than or equal to 0.1 g/l) of monoclonal kappa chains in the urine. In all cases there was an infiltration of the bone marrow by plasma cells containing kappa chains but no heavy chains. A retrospective analysis was made of 126 consecutive cases of Bence Jones myeloma. The number of kappa and lambda cases was approximately the same. All cases secreting less than or equal to 0.1 g light chains per 1 urine were of kappa type. This contrasts with a kappa/lambda ratio of 1.4-1.9 among reported series of M-components containing both heavy and light chains. A review of reported cases of non-secretory myeloma revealed a preserved capacity for Ig synthesis in the majority of cases and among these a preponderance of kappa chain producing clones. These observations might be explained by a higher tendency for kappa chain producing cells to mutate to low secretors or to cells producing abnormal light chains which are catabolized rapidly. The clinical data from our patients do not indicate a more pessimistic prognosis in non- or low-secretory myeloma, than in other cases of multiple myeloma.

Distribution of immunoglobulin-containing cells in bone marrow and lymphoid tissues in patients with monoclonal gammapathy

Cell suspensions of bone marrow and lymphoid tissue from 85 patients with monoclonal gammapathy were investigated by a direct immunofluorescence procedure for the detection of intracellular immunoglobulin alpha, mu, gamma, kappa and lambda chains. Serum Ig levels were determined and daily syntheric rates estimated. In all cases the majority of Ig-containing bone marrow cells contained the same Ig class as that of the M-component in serum or urine indicating a diffuse distriubtion of these clones in the bone marrow. This was observed not only in myeloma but also in benign monoclonal gammapathy (BMG) and lymphoma with an M-component. The M-component producing clone could be traced to extramedullary lymphoid tissue in myeloma but usually not in BMG. A positive correlation was found between the calculated synthetic rate of the M-component and the number of Ig-containing cells in the bone marrow and some indication was found that the synthetic rate per cell might be lower in IgM and IgG than in IgA monoclonal gammapathy. The depressed level of polyclonal Ig in myeloma and to some extent in BMG was parallelled by a diminished number of Ig-containing cells in the bone marrow.

Characterization of cells of the B lineage in the human adult greater omentum

Peritoneal B cells and their omental precursors play an important role in the immune response of the peritoneal cavity and mucosal surfaces in mice. We have previously shown that peritoneal and mucosal B lineage cells are unlikely to be significantly linked in humans. However, the status of the omentum remains unknown. Here, using immunohistochemistry, we observed that sparse, quiescent B cells and occasional clusters of B cells were present in the omentum and that plasma cells, predominantly with cytoplasmic immunoglobulin G (IgG), were present. We analysed sequences of immunoglobulin genes amplified using reverse transcriptase-polymerase chain reaction (RT-PCR) from the normal human greater omentum, and describe the characteristics of variable region genes used by IgG, IgA and IgM. We focused on the properties of IgVH4 and IgVH5 families to allow comparisons of like with like between different Ig isotypes and cells from different immune compartments. We observed that the IgM genes were derived from a mixed population with mutated and unmutated immunoglobulin sequences. All IgVH4 and IgVH5 genes used by IgA and IgG from omental cells showed evidence of somatic hypermutation but the load of mutations was not significantly different to that seen in either the systemic or the mucosal compartments. The trends observed, including the dominance of IgG plasma cells, the IgA1/IgA2 ratio being biased towards IgA1, JH1 usage, and a moderate level of somatic mutations, link omental B lineage cells with the systemic compartment. These observations reinforce previous studies highlighting the difference between human and murine B-cell compartments and their relationship to the mucosal immune system.

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.

Hypermutation, diversity and dissemination of human intestinal lamina propria plasma cells

In this work we have microdissected lamina propria plasma cells and used polymerase chain reaction and sequencing to investigate immunoglobulin (Ig) gene rearrangements and mutations in human intestine. In addition, specific primers were designed for individual Ig gene rearrangements to analyze the distribution of related B cell and plasma cell clones at different sites along the bowel. Confirming our earlier work, intestinal IgVH genes were highly mutated in plasma cells from older individuals (> 30 years). IgVH genes were significantly less mutated in samples taken from patients aged 11-30 years, and there were fewer mutations again in samples from young children (< 11 years). In age-matched specimens the number of mutations was equivalent in the duodenum and colon. Using complementarity-determining region 3 primers to amplify specific Ig gene rearrangements, evidence was also found for the existence of related lamina propria plasma cells along the small bowel and colon, although these were quite scarce. In addition, analysis of the numbers of related clones in a random sampling from discrete areas of lamina propria indicates that the local population is diverse. These results suggest that the highly mutated IgVH genes in adult intestinal plasma cells are a consequence of chronic antigen exposure with age. Duodenal plasma cells are as highly mutated as colonic plasma cells, despite the fact that the upper bowel has no indigenous microbial flora (the stimulus for intestinal plasma cells). They also show that the plasma cell population is diverse and can be widely disseminated along the bowel.

Evaluation of different lymphoid tissue sources for the construction of human immunoglobulin gene libraries

BACKGROUND

Phage display technology allows the isolation of novel human monoclonal antibodies. The technology relies on the construction of a recombinant antibody library and its display on phage particles. The quality of an antibody library is affected by several factors including the size, diversity and source of immunoglobulin genes.

OBJECTIVE

The aim of the project was to determine the best tissue source for the construction of antibody libraries.

STUDY DESIGN

Three tissue sources were used in this study: peripheral blood mononuclear cells from a healthy donor, Epstein-Barr virus (EBV) transformed peripheral blood mononuclear cells and lymph node tissue from individuals with breast cancer. The quality of each tissue source was assessed using two criteria: (1) the number of mature and activated B cells in each source; (2) the amount of immunoglobulin heavy and light chain genes amplifiable by polymerase chain reaction (PCR).

RESULTS

EBV-transformed peripheral blood mononuclear cells and lymph node tissue were shown to contain more B cells than peripheral blood mononuclear cells. A relatively larger amount of immunoglobulin gene products could be amplified from EBV-transformed peripheral blood mononuclear cells and the lymph node. However, immunoglobulin containing gamma 1 chains could not be amplified from EBV-transformed mononuclear cells, and the resultant pattern of gene amplification suggests a possible selection bias.

CONCLUSION

This study indicates that among the three tissue sources examined, lymph node tissue is the most suitable source for the construction of antibody libraries.

Sequence analysis of human IgVH genes indicates that ileal lamina propria plasma cells are derived from Peyer's patches

The origin of human ileal lamina propria (LP) plasma cells has been investigated using a technique based on microdissection of cells from immunohistochemically stained tissue sections. We have sequenced rearranged IgVH4.2 1, IgVH 5 family and IgVH6 genes from Peyer's patch germinal center (GC) cells and plasma cells from the ileal LP. Clonally related cells were identified by comparison of their complementarity determining region (CDR) 3 sequences and patterns of somatic mutation. We observed Ig genes from B cells in the GC of Peyer's patches which were related to Ig genes from plasma cells in the ileal LP, demonstrating that clonally related cells span these sites. In addition, groups of clonally related. but diversified plasma cells were common in the lamina propria. All Ig genes isolated from LP plasma cells were heavily mutated. The distribution of mutations in the CDR of the Ig heavy chain variable region (VH) genes which were considered to be the expressed alleles in LP plasma cells was consistent with an affinity-matured response. These observations provide compelling evidence for the origin of human ileal plasma cells from the Peyer's patches.

Spondylarthropathies: from gut to target organs

Recent studies strongly support the concept that gut and joint inflammation are closely related. Progress also has been made in identifying individual mechanisms that contribute to the pathogenesis of joint disease in IBD and in undifferentiated SpAs. However, the interrelationship of these mechanisms that result in chronic disease manifestations at a site distant from the initiating event remain to be elucidated. The local absence of homing molecule receptors in the gut wall combined with an expression of these receptors in target organs can be responsible for the transformation of the synovial membrane and/or the enthesis into an aberrant tertiary lymphoid organ of the gut.

Distribution characteristics of immunoglobulin-secreting cells in adenoids. Relationship to age and disease

Forty-four adenoids and 52 palatine tonsils from 71 children and adolescents (age 3-21 years) undergoing surgery because of adenoidal hypertrophy or recurrent tonsillitis were examined for the presence of immunoglobulin-secreting cells (ISC) employing an enzyme-linked immunospot assay (ELISPOT). ISC constituted less than 2% of the mononuclear cell population. Adenoids contained IgG, IgA, and IgM ISC in significantly lower numbers than palatine tonsils. The predominant isotype of the ISC was IgG, in adenoids accounting for 62% of the ISC and in palatine tonsils for 73%. The relative numbers for IgA and IgM ISC were similar. A significant correlation existed between autologous adenoids and palatine tonsils for the numbers of IgA and IgM ISC, but not for the numbers of IgG cells. These observations suggest that, adenoid and palatine tonsils display similar immunoglobulin distribution patterns within a single individual. However, individuals with hypertrophied adenoids exhibited a numeric decrease in IgG ISC with increasing age (P less than 0.01). Both lymphoid tissues may be involved in mucosal immune defense.

Murine intestinal antibody response to heterologous rotavirus infection

Rotavirus is the most important worldwide cause of severe gastroenteritis. Extensive efforts have been devoted to the design of a vaccine that will prevent disease, but development of a more effective vaccine strategy may require progress in the understanding of the mucosal immune response to replicating viral antigens. In this article, we report the characterization of the intestinal antibody response of a murine model to heterologous infection with the rhesus rotavirus vaccine strain. We have adapted the enzyme-linked immunospot assay to measure this response without the difficulties associated with measurement of antibodies in intestinal contents or the artifacts associated with culturing of lymphocytes. The predominant response in terms of antibody-secreting cells (ASC) is seen in the small intestine lamina propria, which can be measured within 4 days of infection, peaks 3 weeks after infection, and remains near that level for longer than 8 weeks. The magnitude of the immunoglobulin A (IgA) cell response is approximately 10 times greater than the intestinal IgG cell response, and IgM cells are rare. Virus-specific ASC constitute approximately 50% of all ASC in the gut at the peak of the virus-specific response. This response is considerably greater than responses to nonreplicating mucosal antigens measured by similar techniques. Enteral infection engenders minimal virus-specific ASC response in the spleen. Rhesus rotavirus-specific enzyme-linked immunosorbent assay and neutralization assays of serum and intestinal contents did not correlate with virus-specific ASC response.

Monoclonal gammopathies in children

Over a 10-year period sera of 4000 pediatric patients were subjected to agar gel electrophoresis and immunoelectrophoresis. Retrospective examination of the electrophoresis patterns indicated that single or multiple homogeneous immunoglobulin components were present in sera of 155 children (3.9%). They were most frequently found in patients suffering from primary and secondary immunodeficiency diseases, hematological malignancies, autoimmune diseases, and severe aplastic anemia. Follow-up analysis revealed that most of these monoclonal gammopathies were transient. The monoclonal gammopathies in the serum of 79 patients were identified by immunoblotting for class and light-chain isotypes. A marked absence of IgA monoclonal gammopathies and a predominance of monoclonal gammopathies of the lambda light-chain isotype were found. Most of the B-cell mono- or oligoclonal proliferations in children can probably develop due to a disturbance in the regulatory T-cell function.

Polymeric and monomeric IgA response in serum and milk after parenteral cholera and oral typhoid vaccination

The effect of vaccinating lactating Pakistani mothers with a combination of live oral typhoid vaccine and parenteral inactivated cholera vaccine on specific milk and serum IgA antibodies in both monomeric (m) and polymeric (p) forms was analysed. IgA antibody titres peaked for both antigenic specificities 2 weeks after the first dose of vaccine. 82 +/- 7% of anti-Vibrio cholerae and 72 +/- 17% of anti-Salmonella typhi IgA were in the polymeric form. These serum pIgA antibodies were mainly dimeric IgA, not complexed with the secretory component. They disappeared more rapidly from serum than mIgA antibodies. Anti-V. cholerae IgA responses were parallel in serum and milk samples, whereas anti-S. typhi responses were dissociated. In milk, IgA antibodies were secretory IgA for both antigenic specificities, being probably of local origin in the mammary gland. Our results indicate that both oral and parenteral vaccinations can induce pIgA antibodies in serum and secretions, confirming that the presence of pIgA in serum does not necessarily reflect an immune stimulation only at the mucosal level.

Human bone marrow-derived IgA is produced by IgA-committed B cells in vitro

Although human bone marrow has been implicated in the production of serum immunoglobulins, little information is available concerning the kinetics of antibody production (primary- or secondary-type humoral response) or the cells that are responsible for antibody production in human bone marrow. In this study, the kinetics of and cells responsible for antibody production in the bone marrow were investigated. Previous studies have demonstrated that human bone marrow mononuclear cells secrete a significant amount of IgA in vitro. This finding led to the focus of the present investigation on bone marrow IgA production. The results reported here demonstrate that IgA was synthesized de novo in cultures of bone marrow mononuclear cells; its peak concentration in the culture supernatants preceded that of IgM; its production was totally inhibited by the addition of microgram quantities of anti-alpha-chain antiserum, while milligram quantities of anti-mu-chain antiserum were required for even partial inhibition of IgA production; and the culture of isolated IgA-bearing cells resulted in a greater than 13-fold increase in IgA concentration in the culture supernatants as compared with those from unseparated bone marrow mononuclear cells. From this study, it was concluded that bone marrow produces IgA as a secondary or anamnestic response to some undetermined stimulus and that IgA-committed B cells residing in, although probably not stimulated in, the bone marrow compartment were responsible for the IgA synthesis and secretion in vitro.

Bone marrow Ig-secreting cells in patients with malignant lymphoma

Bone marrow immunoglobulin (Ig)-secreting cells of three major Ig classes were quantitated in patients with malignant lymphoma with or without definite bone marrow invasion, using a protein A hemolytic plaque assay. The mean percentage of each class of Ig-secreting cells in patients without bone marrow invasion was 77% for IgG, 17% for IgA, and 6% for IgM, whereas it was 86% for IgG, 6% for IgA, and 8% for IgM in patients with definite bone marrow invasion. An increase in bone marrow Ig-secreting cells of the same Ig class that is detected on the surface of lymphoma cells and that is consistent with the concentration of the same serum monoclonal Ig is considered to indicate the presence of metastatic lymphoma cells in the bone marrow. A decrease in the percentage of bone marrow IgA-secreting cells was a consistent feature in patients with definite bone marrow invasion.

Bone-marrow plasmocytosis--an immunohistological study

Bone-marrow biopsies and smears from 59 patients with reactive plasmocytosis (22), multiple myeloma (24), solitary plasmocytoma (3) and monoclonal gammopathy of undetermined significance (MGUS) (10) were examined. To demonstrate cytoplasmic immunoglobulin the immunoperoxidase method was applied and evaluated quantitatively. Immunohistology yielded different ranges in kappa/lambda ratio for reactive plasmocytosis (0.4-3.5), multiple myeloma (less than or equal to 0.1 and greater than or equal to 11.2) and MGUS (0.2-3.0). As a result this method seems to be helpful in characterizing a plasmocytosis and distinguishing overt myeloma from monoclonal gammopathy of undetermined significance and reactive plasmocytosis. A differentiation of monoclonal gammopathy of undetermined significance from reactive plasmocytosis is not possible histologically and immunohistologically.

Lymphocyte function in human bone marrow. III. Isotype commitment, metabolic and secretory characteristics of immunoglobulin producing cells

We have examined the functional and metabolic properties of immunoglobulin (Ig)-secreting cells in adult (rib) bone marrow, the tissue which provides the major proportion of serum Igs. In the absence of polyclonal activators, high rate Ig production (1-2 micrograms/day/10(6) marrow mononuclear cells) was sustained from the beginning of culture throughout 2 weeks and then declined. Ten percent of the Ig secreted was of the IgM isotype and IgG/A made up the remainder at equal proportions. Infection of marrow cells with Epstein-Barr virus (EBV) induced the production of large amounts of IgM, but virtually all IgG/A-committed cells were refractory to stimulation with EBV. Both EBV-induced and the "spontaneous" Ig production was inhibited by cycloheximide, but only EBV-induced IgM production was blocked by hydroxyurea and gamma-irradiation. The polyclonal activators PHA and PWM induce suppressor-T-cell activity in marrow cultures. This suppressor function involves nonproliferating cells which acquire suppressive activity 3-4 days after mitogenic activation. Prednisolone and cyclosporine A modulate Ig production in cultures of peripheral lymphocytes but had no effect on Ig secretion in marrow cell cultures. This observation was reminiscent of the absent or at best marginal short-term effects on in vivo serum Ig levels which is typical for these drugs. Our observations suggest that the marrow Ig-producing B-lymphoid cell compartment shows major differences to other tissue sites with respect to properties of the Ig-secreting cells the immunoregulatory activities able to control their function, and the response of these cells to clinically important drugs.

The human gastrointestinal secretory immune system in health and disease

The main function of secretory IgA is to exert immune exclusion; that is, by intimate cooperation with innate non-specific defence mechanisms, it dampens down penetration of soluble antigens and inhibits epithelial colonisation of bacteria and viruses. Secretory IgM may exert a similar protective function in the gut as its local synthesis sometimes is markedly increased, especially in selective IgA deficiency. IgG should not be considered a secretory immunoglobulin because its external translocation depends on passive intercellular diffusion. By activating complement, antibodies of this isotype may cause increased mucosal permeability and tissue damage. IgG may thus contribute to persistent immunopathology in mucosal lesions. The same is true for IgE antibodies which, in atopic individuals, may be carried into the gut mucosa by mast cells and cause their degranulation with histamine release. Secretory IgA and secretory IgM are the products of two cell types: plasma cells synthesise IgA dimers and IgM pentamers which, by non-covalent association, become complexed with the secretory component (SC) which is synthesized by serous-type glandular cells. The adsorption of the Ig polymers to the SC-expressing epithelial cells depends on J chain-determined binding sites. This fact gives biological significance to the striking J chain expression shown by mucosal immunocytes regardless of the Ig class they produce. The immunocytes populating the gut mucosa apparently belong to relatively early memory B cell clones. The obvious functional goal of J chain expression at this stage of clonal differentiation is local generation of SC-binding IgA and IgM polymers. In various gut diseases, altered immune regulation results in a disproportionately increased number of J chain-negative IgG-producing cells in the mucosa. Such altered immunological homeostasis may contribute to perpetuation of inflammatory bowel diseases.

Bone marrow histopathologic patterns and immunologic findings in B-chronic lymphocytic leukemia

In 82 patients with B-chronic lymphocytic leukemia, the correlations between the histopathologic bone marrow patterns (interstitial, nodular, mixed, and diffuse), serum immunoglobulin (Ig), and blood B-lymphocyte levels and T-lymphocyte levels have been analyzed. The most commonly lowered Ig class was IgM (43% of cases) followed by IgA (35%), and IgG (10%). There was a trend to a more frequent decrease of Ig levels when "advanced" bone marrow patterns (mixed + diffuse) were compared with the earlier ones (interstitial + nodular). The frequency of such a decrease was statistically significant for IgA class (P less than 0.01). The absolute number of blood T-lymphocytes was increased in the diffuse pattern (P less than 0.01).

Immunoglobulin A nephropathy. Quantitative immunohistomorphometry of the tonsillar plasma cells evidences an inversion of the immunoglobulin A versus immunoglobulin G secreting cell balance

Primary IgA nephropathy (Berger's disease) is characterized by renal deposits of IgA, the origin of which is still unknown. However, several clinical and biological findings suggest that these immunoglobulins might have a mucosal origin, and that such patients should present mucosal abnormalities. This paper reports the results of the immunohistomorphometrical analysis of tonsillar plasma cells from seven patients suffering from Berger's disease and seven controls also with recurrent tonsillitis. IgG, IgA, and IgM-secreting cells were enumerated after immunofluorescent staining of serial frozen-cut sections from 20 tonsils. In controls, a predominance of the IgG-secreting population, similar to this reported in the literature was observed (65% of IgG secreting cells and 29% of IgA plasma cells), while an inversion in the patients' plasma cells percentages was evidenced (IgG:37%, IgA:56%). This increment in the IgA population was paralleled by an augmentation of the number of dimeric IgA-secreting cells (75% of IgA plasma cells), stained both for cytoplasmic IgA and J chain. In controls, the latter cells were in similar proportions as previously reported by others (45% of IgA plasma cells). These results demonstrate an imbalance in the IgA-producing system of patients with Berger's disease, which is in keeping with the hypothesis favoring a mucosal origin for the mesangial IgA present in their kidneys.

Comparison of the sensitivity of the protein A plaque assay and the immunofluorescence assay for detection of immunoglobulin producing cells

This paper reports a comparative study on the sensitivity of the protein A plaque assay and the cytoplasmic immunofluorescence assay for detection of immunoglobulin (Ig) producing cells in cell suspensions of murine lymphoid organs. The protein A plaque assay was found to detect as many or several times more Ig producing cells than the immunofluorescence assay, depending on the age and antigenic load of the mice, and upon the Ig class and organ studied.

Quantitative study of the immunoglobulin-containing cells in trephine samples of bone marrow

Immunoglobulin (Ig) was demonstrated in paraffin sections of 12 trephine bone marrow biopsies by means of the unlabelled antibody peroxidase-antiperoxidase (PAP) method. The Ig-containing cells, which were counted with the Reichert-Jung (Kontron) MOP-AMO(3) user-controlled image-analyser, were found to constitute approximately 4.2% of all the nucleated cells in the marrow, a figure significantly higher than those reported by previous workers.

Intestinal salivary, and tonsillar IgA and J-chain production in a patient with severe deficiency of serum IgA

An 18-year-old man with tendency to respiratory infections had a serum IgA level of only 2% of normal whereas his salivary IgA amounted to 50% of the lower normal concentration range. Moreover, both the rectal and jejunal IgA-producing cell populations were of normal size. Nevertheless, a relative increase of salivary IgM and a distinctly raised number of IgM-producing cells in jejunal mucosa indicated an imbalance in his secretory immune system. This possibility was supported by the presence of an excess of J 3 chains in most of his intestinal IgA immunocytes, probably reflecting a reduced synthetic rate of IgA. The number of tonsillar IgA-producing cells was only slightly below the normal range; most of them lacked J chain, as normal, and could thus be a source of his serum IgA, which was mainly monomeric. A marked deficiency of IgA-producing cells in his bone marrow supported the notion that this tissue site normally is the major source of monomeric IgA. This study suggests that a generally defective IgA system may be topically activated owing to the persistent antigenic and mitogenic load on mucosa-associated lymphoid tissues. Our findings are not consistent with a general regulative compartmentalization of monomer- and dimer-producing IgA immunocyte populations.

Influence of age on the immunological activity and capacity of the CBA mouse

The immunological activity and capacity were studied in the CBA mouse as a function of its age. The activity was determined by the number of immunoglobulin containing (C-Ig) cells in different lymphoid organs and the immunoglobulin levels of the serum in non-artificially stimulated animals. It was confirmed that in older age the bone marrow takes over from the spleen the role of the major site of immunoglobulin production. A clear decrease in the number of C-Ig cells was observed in the mesenteric lymph nodes and the Peyer's patches. The Ig serum remained constant after the sixth month of age, with the exception of an increase of IgG1 and IgG,2B. There was a striking increase in variation between the individual animals with advancing age. From these data it can be concluded that the B-cell system of old animals is as active as that of young adult animals. The immunological capacity of CBA mice of various ages was assessed by measuring the levels of specific antibodies after the administration of human serum albumin in complete Freund's adjuvant. A severe decline of the primary and the secondary response was observed on ageing. The reaction of three year old animals was negligible. The discrepancy between the declining immunological capacity and the constant or increasing immunological activity is explained by an age-related deficiency of the T-cell compartment in the spleen.