IgA and IgM rheumatoid factors in serum, saliva and other secretions: relationship to immunoglobulin ratios in systemic sicca syndrome and rheumatoid arthritis.

Paired serum and saliva samples from seven patients with systemic sicca syndrome (SSS), 15 patients with rheumatoid arthritis and a positive Schirmer's test (RA+), 15 patients with rheumatoid arthritis and negative Schirmer's test (RA-) and 14 normal individuals were analysed for albumin and immunoglobulin concentration as well as IgA and IgM rheumatoid factor (RF) activity. Protein levels in saliva were higher in SSS and RA+ but, when corrected for serum concentration and salivary flow rate, only the IgG ratio remained significantly elevated in SSS (P less than 0.01) and RA- (P less than 0.05) and the IgM ratio was reduced in RA- (P less than 0.05) compared to controls. Although IgM RF activity in serum and saliva was strongly correlated (P less than 0.001) in all three patient groups, the activity in saliva was considerably lower than serum activity. In the two (RA) patients tested, IgM RF in saliva contained secretory component. Mean salivary IgA RF activity varied between 34% (RA-) and 84% (SSS) of serum activity and correlated with serum activity in SSS (P less than 0.001) and RA- (P less than 0.01). IgA RFs in saliva, but not in serum, contained secretory component. Additional demonstration of IgA RF activity in nasal and duodenal secretions in SSS may be related to involvement of the common mucosal immune system.     

Deficient repair of O6-methylguanine in lymphocytes from rheumatoid arthritis families may be an acquired defect.

Deficient repair of the premutagenic DNA lesion O6-methylguanine (O6-MeGua) has been reported in lymphocytes from patients with autoimmune diseases. This was confirmed in the present study of probands with rheumatoid arthritis (RA) and their families. We also noted a significant deficiency in 9/19 spouses (P less than 0.05) and a statistically non-significant deficiency of repair of O6-MeGua in 14/42 first and second degree relatives in comparison with healthy and non-autoimmune disease controls, respectively. A significant correlation of the repair status of O6-MeGua in DNA between individual probands with RA and respective spouses (P less than 0.01) and probands and respective family members (P less than 0.001) supported the idea that an environmental, transmissible agent could influence the expression of the protein, O6-methylguanine-DNA-transferase (O6-MT), involved in the repair of O6-MeGua. The present results, however, cannot entirely exclude an additional hereditary influence.     

A quantitative assay for IgA rheumatoid factor

We have developed a solid-phase radioimmunoassay capable of detecting nanogram quantities of human IgA rheumatoid factor (RF) in biological fluids. Human IgM RF, IgG RF, IgG, IgA, IgM and whole serum did not significantly interfere with the IgA RF assay. Patients with sero-positive rheumatoid arthritis (RA) had significantly higher concentrations of IgA RF than sero-negative RA patients or healthy adult controls. Concentrations of IgA RF in paired sera and synovial fluids from sero-positive RA patients were comparable. Levels of IgA RF demonstrated a moderately good correlation with levels of IgM RF in sero-positive RA sera (r = 0.673). However, the ratio of IgA RF concentration to IgM RF concentration in sero-positive RA sera varied widely.     

Re-evaluation of ELISA and latex agglutination test for rheumatoid factor detection in the diagnosis of rheumatoid arthritis.

An indirect ELISA for the determination of each isotype (IgM, IgG, IgA, IgD, IgE) of rheumatoid factors (RF) was performed with sera obtained from 77 patients with either classical or definite rheumatoid arthritis (RA) and 319 controls, using rabbit IgG as the antigen. The results were compared with those of a commercial latex agglutination test, using denatured human gamma globulin as the antigen for rheumatoid factor determination. At the cut-off level at which positive results were found in less than 5% of normal controls, ELISA for IgM RF determination had sensitivity, specificity, efficiency, positive predictive value and negative predictive value of 46.75%, 98.12%, 88.13%, 85.71%, 88.41%, while those for IgA RF were 46.75%, 93.42%, 84.34%, 63.16%, 87.91% and for IgG RF were 59.74%, 92.16%, 85.86%, 64.78%, 90.46%, respectively. These indices by latex agglutination test were 83.11%, 93.73%, 91.67%, 76.19% and 95.83%, respectively. IgD RF titre greater than or equal to 1:5 was detected in 19/77 RA patients and 4/200 normal controls while IgE RF titre greater than or equal to 1:5 was detected only in 7/77 RA patients. Thus, ELISA did not appear to have any advantage over latex agglutination test for diagnosis of RA.     

In vitro immunoglobulin production by mononuclear cells in rheumatoid arthritis

Since patients with rheumatoid arthritis (RA) exhibit serum hypergammaglobulinemia and autoantibody (rheumatoid factor) production, we compared elaboration and control of in vitro RA mononuclear cell (MNC), Ig assayed by enzyme-linked immunoassays or by hemolytic plaque formation, in 37 RA patients and 17 normal subjects. We found (1) RA spontaneous plaque-forming cells were significantly reduced (RA 344 vs normal 627 PFC/10(6) MNC, P less than 0.002); (2) RA spontaneous IgG and IgM (but not IgA) elaboration was significantly diminished (IgG RA 339, normal 776; IgM RA 255, normal 869 ng/ml, P less than 0.001; IgA RA 87, normal 124); (3) RA stimulated IgG and IgM production (but not IgA) was also decreased (IgG RA 2434, normal 3862, P less than 0.06; IgM RA, 1676, normal 3323, P less than 0.005; IgA RA 1859, normal 2315); (4) reduced RA Ig elaboration was not clearly due to altered numbers of T or non-T cells, age, medications, clinical features of disease, or response kinetics; (5) relative improvement of RA in vitro IgG, but not usually IgM, secretion followed removal of adherent cells, addition of indomethacin or addition of mitomycin C-treated T cells; (6) MNC from synovial fluids, but not bone marrows, exhibited spontaneous Ig production in excess of stimulated synovial fluid cellular or peripheral blood Ig elaboration. These observations indicate selective impairment of peripheral blood MNC IgG and, particularly, IgM secretion in RA. This defect appears to reflect accessory cell influences which differ from normal as well as the sequestration of primed or activated cells in the synovial fluid.     

IgM rheumatoid factor elaboration by blood, bone marrow, and synovial mononuclear cells in patients with rheumatoid arthritis

IgM rheumatoid factor (RF) elaboration by rheumatoid arthritis (RA) synovial, bone marrow, and blood mononuclear cells (MNC) is reported. IgM RF was prepared from RF-positive sera by sequential euglobulin precipitation, Sephacryl S300 gel filtration, and IgG-Sepharose affinity chromatography. Purified material, which contained no detectable IgG or IgA, was used in an enzyme-linked immunosorbent assay (ELISA) to quantitate cellular elaboration of IgM RF. Excellent standard curves (r2 = 0.98) were obtained without nonspecific binding of samples or antisera to IgG-coated microtiter plates and without cross-reactivity of standards with antisera other than anti-IgM. We found RA blood MNC (11 patients) spontaneously averaged 15 ng/ml IgM RF (6% of total IgM produced), but elaborated 254 ng/ml IgM RF following pokeweed mitogen (PWM) stimulation (22 patients), exceeding that of 13 normal controls. Bone marrow MNC spontaneously (4 patients) produced 71 ng/ml IgM RF and secreted 78 ng/ml IgM RF with PWM stimulation (9 patients). In contrast synovial fluid MNC (5 patients) spontaneously elaborated 6652 ng/ml IgM RF, significantly (P less than 0.05) more than blood or bone marrow MNC; PWM-stimulated synovial fluid MNC (5 patients) produced 5472 ng/ml IgM RF. These observations confirm selective localization of activated, IgM RF-producing cells to the rheumatoid synovial space.     

Measurement of Rheumatoid Factor Isotypes in the Clinical Laboratory

In this study we assessed the clinical utility of measuring all major rheumatoid factor (RF) isotypes (IgG, IgA, and IgM) in the diagnostic immunology laboratory using an enzyme-linked immunoassay (ELISA). An improved method for IgG-RF was tested which employed a commercially available monoclonal anti-human IgG Fd antibody and did not require pepsin digestion of samples. We detected elevated levels of all three RF isotypes in a population of hospitalized rheumatoid arthritis patients (n=109). We demonstrated a significant association between IgM and IgA RF which occurred in 36% of our subjects, while less than 6% had IgM + IgG RF or IgG + IgA RF. A comparison of the IgM ELISA with the Rheuruaton revealed a statistically significant correlation (r=0.65, p=0.0001). In addition, the two methodologies were equivalent in sensitivity (ELISA: 76%, Rheumaton: 78%). However, the ELISA procedure was more time consuming, costly, and required greater technical expertise. The following clinical and laboratory findings were significantly associated with RF isotypes: IgG RF and the presence of rheumatoid nodules (p=0.03), elevated erythrocyte sedimentation rate (ESR) and IgG RF (p=0.007), and elevated ESR and IgM RF (p=0.0009). Our ELISA methodology did not provide significant advantages over existing techniques to justify its use as part of the routine laboratory assessment of rheumatoid factor.     

Measurement of Rheumatoid Factor Isotypes in the Clinical Laboratory

In this study we assessed the clinical utility of measuring all major rheumatoid factor (RF) isotypes (IgG, IgA, and IgM) in the diagnostic immunology laboratory using an enzyme-linked immunoassay (ELISA). An improved method for IgG-RF was tested which employed a commercially available monoclonal anti-human IgG Fd antibody and did not require pepsin digestion of samples. We detected elevated levels of all three RF isotypes in a population of hospitalized rheumatoid arthritis patients (n=109). We demonstrated a significant association between IgM and IgA RF which occurred in 36% of our subjects, while less than 6% had IgM + IgG RF or IgG + IgA RF. A comparison of the IgM ELISA with the Rheuruaton revealed a statistically significant correlation (r=0.65, p=0.0001). In addition, the two methodologies were equivalent in sensitivity (ELISA: 76%, Rheumaton: 78%). However, the ELISA procedure was more time consuming, costly, and required greater technical expertise. The following clinical and laboratory findings were significantly associated with RF isotypes: IgG RF and the presence of rheumatoid nodules (p=0.03), elevated erythrocyte sedimentation rate (ESR) and IgG RF (p=0.007), and elevated ESR and IgM RF (p=0.0009). Our ELISA methodology did not provide significant advantages over existing techniques to justify its use as part of the routine laboratory assessment of rheumatoid factor.     

Prevalence of anti-Fab antibodies in patients with autoimmune and infectious diseases.

Sensitive ELISA were devised to examine the specificity of circulating IgM and IgA autoantibodies for whole human IgG, Fc and Fab fragments of human IgG. Sera from patients with autoimmune and infectious conditions such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), tuberculosis (TB), infectious mononucleosis (IM) and cystic fibrosis (CF) were studied. Results of the ELISA assays using whole human IgG as antigen revealed that a proportion of patients in each of the groups studied had circulating IgM and IgA rheumatoid factors (RF). Fifteen normal individuals studied were negative. In the latex positive RA group, IgM RF and IgA RF had primarily anti-Fc reactivity (100% and 93% respectively), although 3/15 patients also showed IgM anti-Fab reactivity and one patient had high IgA anti-Fab activity. Patients with SLE and TB who had detectable RF levels also revealed predominantly anti-Fc specificity. In contrast, examination of 25 patients with IM showed positivity for IgM RF activity in 8% of patients using whole IgG as antigen, 24% positivity using purified Fc fragments as antigen and 45% positivity when plates were coated with Fab fragments. Similarly, a large number of CF patients (54%) also showed predominantly IgM anti-Fab activity. Of interest, 69% of the CF patients who were all studied at the time of bacterial infection had detectable IgA RF levels, with 46% of these patients showing both IgA anti-Fc and anti-Fab activity. These findings suggest that autoantibody specificities in autoimmune and infectious diseases are different.     

Rheumatoid arthritis-associated antibodies in healthy first-degree relatives of RA patients

Rheumatoid arthritis (RA) affects approximately 1.5% of the population worldwide and 0.5–3.3% of the Mexican population. The presence of rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPA) and anti-carbamylated protein (anti-CarP) antibodies has been described in populations at risk of RA development, such as first-degree relatives (FDR). Anti-CarP antibodies are present in RA patients (44%), FDR of RA patients (18%) and healthy controls (4.7%). Anti-CarP antibodies have not been described in FDR of the Mexican population. The objective of this study was to determine the prevalence of Rheumatoid Factors (RF) isotypes, ACPA and anti-CarP antibodies isotypes in FDR of RA patients. An observational, cross-sectional study, in an FDR of RA cohort, was performed. We measured IgA, IgG and IgM isotypes of RF, ACPA and anti-CarP antibodies. A total of 144 FDRs from 99 RA patients were enrolled. The prevalence of anti-CarP antibodies was 2.8% for IgA, 4.2% for IgG, whereas IgM was not detected. The serologic association was for RF/ACPA 4.48%, RF/anti-CarP 2.7%, FR 64.5%, ACPA 1.3%, ACPA/anti-CarP 0.69%, anti-CarP 3.4%, and no RF/ACPA/anti-CarP was observed. We found a low prevalence of anti-CarP antibodies in our cohort of FDR of RA patients, but the prevalence of ACPA and RF were higher than other cohorts previously reported.     

IgA rheumatoid factor and IgG dietary protein antibodies are associated in rheumatoid arthritis

This study sought to determine whether patients with rheumatoid arthritis (RA) were immunologically sensitised to dietary protein (DP). Using an enzyme linked immunosorbent assay (ELISA), antibodies to milk and wheat proteins were measured in 93 unselected out-patients with classical or definite RA. Of these 93, 53 had raised levels of IgG antibodies to one or both dietary proteins (DP). In the DP antibody positive group, 48 patients (90%) also had raised levels of IgA rheumatoid factor (measured by ELISA) while only 7 (17%) of the 40 DP antibody negative patients had detectable IgA RF; P less than 0.02. There was no association between IgM rheumatoid factor and dietary protein antibodies. These results demonstrate that in RA, raised levels of IgA RF are associated with an increased IgG response to antigens which enter the body through the gastrointestinal tract. A breakdown in gastrointestinal tolerance to dietary antigens may play a role in the immunopathogenesis of RA in these patients who might therefore benefit from dietary manipulation.     

Dot-blot ELISA for the detection of IgM RF and IgA RF.

Dot-blot ELISA was developed for the detection of IgM RF and IgA RF. Normal rabbit IgG (NRIgG), concentration 100 micrograms/ml, was used as the antigen for dotting on the 0.45 microns pore size nitrocellulose membrane. Serum, conjugate and substrate incubation conditions were at room temperature for 1 hour, 1 hour and 3 minutes, respectively. The membrane with NRIgG dot could be sotred for 6 weeks before use in the assay. Positive results of IgM RF, at the serum dilution 1:800, were found in 31/51 patients with either classical or definite rheumatoid arthritis and 3/68 normal healthy individuals. Positive IgA RF, at the serum dilution 1:100, was found in 27/51 of the former and none of the latter. Significant concordance with high agreement index was found between the results of the dot-blot ELISA developed and those obtained from ELISA performed in microtitre plate (Kappa greater than or equal to 0.78 for IgM RF and 0.83 for IgA RF, p less than 0.001).     

HC-IgA antibodies of different specificities are normally present in serum: quantitation by ELISA and relationship to the major Ig classes.

Enzyme-linked immunosorbent assays (ELISA) were developed for direct measurement of protein HC-IgA complexes (HC-IgA) in serum with antibody specificity for rabbit IgG (rheumatoid factor (RF) activity), lipopolysaccharide from Yersinia enterocolitica serotype O:3 (Y3) and tetanus toxoid (TT). About 80% of patients with rheumatoid arthritis had increased concentrations of HC-IgA-RF. The values were correlated with the concentrations of IgA-RF and IgM-RF. HC-IgA anti-Y3 was measured in 45 sera with anti-Y3 antibodies of IgM, IgG and IgA class. The HC-IgA anti-Y3 levels were correlated with those of anti-Y3 of IgG and IgM class, but not of IgA class. For HC-IgA anti-Y3, the closest correlation was that with the specific IgM antibody concentration, rs = 0.63 (p less than 0.001). In 25 normal sera, significant correlations were observed between HC-IgA anti-TT and specific antibodies of IgG and IgA class, but not of IgM class. In 107 sera containing IgA M-components, the total concentration of HC-IgA correlated poorly with both protein HC and with IgA concentrations. It was concluded that specific HC-IgA antibodies are normal constituents of serum, and that their concentrations are not directly related to the serum content of specific IgA antibodies.     

Local IgA and IgM rheumatoid factor production in autoimmune MRL/lpr mice.

Spontaneous local immunoglobulin (IgA, IgG, IgM) as well as IgA and IgM rheumatoid factor (RF) production in salivary glands, lymph nodes, and spleen was analyzed at various ages in autoimmune MRL/Mp-lpr/lpr (MRL/lpr) mice by using an ELISPOT assay. The longitudinal design of the study permitted correlations with severity of disease in salivary glands (sialadenitis). Local production of immunoglobulins in salivary glands and lymph nodes occurred with a pattern of IgG much greater than IgM greater than IgA. This isotype pattern differed from that simultaneously observed in spleen where IgG did not predominate to the same extent. Moreover, the spleen was the major site of IgM production. Rheumatoid factors constituted a significant fraction of local IgA and IgM in involved salivary glands. The pattern of IgA RF isotype expression in salivary glands contrasted with that observed in spleen. While the number of IgA and IgG secreting cells increase at an early age, the peak of RF production in salivary glands occurs in older mice. Furthermore, the level of immunoglobulin secretion was positively correlated with disease severity in salivary glands. The results suggest that local RF production is a secondary event in salivary gland inflammation in MRL/1pr mice rather than an initiating factor in this process.     

MRSPAH: A simple microtitre plate test for rheumatoid factors of different classes

A simple and inexpensive microtitre plate test (the mixed reverse (solid-phase) passive antiglobulin haemadherence test, or MRSPAH) has been developed for the measurement of antiglobulins (RFs) of different classes. Results obtained for IgM RF by this test have been compared with results of latex and Rose-Waaler (DAT) tests on rheumatoid arthritis (RA) sera. Levels of RFs of IgM, IgG and IgA classes have been measured by MRSPAH using rabbit IgG as antigen in RAs and normal people. 94% of RA sera tested were above the upper limit of normal for IgM and/or IgA RF. There was a considerable overlap between IgG RF levels in RAs and normals, although the means of the two groups were significantly different.     

Occurrence of two germline-related rheumatoid factor idiotypes in rheumatoid arthritis and in non-rheumatoid seropositive individuals.

Human rheumatoid factor (RF) paraproteins express two distinct light chain cross-reactive idiotypes defined by the monoclonal antibodies 17.109 and 6B6.6. These germline gene-related cross-reactive idiotypes are both carried on VK3 light chains and are each present on about one-third of IgM RF paraproteins. We assessed the degree to which these idiotypes are represented in polyclonal RFs. We used rheumatoid arthritis (RA) and non-RA RF-positive sera selected from a large cross-sectional population study (the Mini-Finland Health Survey), and sera from a community-based follow-up study of recent-onset RA patients from Heinola, Finland. In the Mini-Finland Health Survey, elevated levels of the 17.109 RF idiotype were seen in sera of 13% of the RA and 19% of the non-RA group; 6B6.6 RF was seen in 26% of the RA and 28% of the non-RA group. In sera of the Heinola follow-up study, 17.109 RF was seen in 12% initially, but in only 3% at 8 years. Similarly, 6B6.6 RF was detected in 25% initially, but in only 7% at 8 years. Ten sera positive for RF prior to the onset of clinical RA were identified from individuals of a second large population study from Finland (North Karelia project); two of these sera exhibited the 6B6.6 idiotype; none exhibited the 17.109 idiotype. The data are consistent with the concept that these germline gene-related cross-reactive RF idiotypes occur frequently in the polyclonal RF of non-RA as well as RA sera, and that in RA the idiotypes may sometimes be reduced or lost as a consequence of somatic diversification of the RF through somatic mutation, usage of new germline genes, or both.     

T-Cell Helper Activity and B-Cell Function of Synovial and Blood Lymphocytes from Patients with Rheumatoid Arthritis or Other Forms of Chronic Arthritis

The helper effect of T cells on B-cell immunoglobulin (Ig) responses induced by pokeweed mitogen (PWM) or purified protein derivative of tuberculin (PPD) was studied in lymphocytes from synovial fluid (SF) and blood of nine patients with rheumatoid arthritis (RA) and eight patients with other forms of chronic arthritis. In PWM cultures the helper effect of SF T cells on Ig responses (IgG, IgM, IgA) of autologous and allogeneic blood B cells was lower than that of blood T cells (P less than 0.01). This decrease was more pronounced in patients with RA than in patients with non-RA. In PPD cultures no significant difference was found between the helper effect of SF T cells and blood T cells on the Ig responses of allogeneic blood B cells or on the IgG response of autologous blood B cells, whereas the helper effect of SF T cells on the IgM and IgA responses of autologous blood B cells was decreased. The Ig responses to PWM or PPD in cocultures of autologous blood B and T cells were not significantly different between patients and healthy controls. The PWM- and PPD-induced Ig responses of SF B cells were lower than those of blood B cells when cocultured with autologous blood T cells. SF B cells produced IgG but usually little IgM and IgA. Thus there was a dysfunction of SF B cells and of SF T cells in a PWM-driven system, but a fairly good helper function of SF T cells in a PPD-driven system.     

Expression of the major rheumatoid factor cross-reactive idiotype in pediatric patients with systemic lupus erythematosus

Rheumatoid factor cross-reactive idiotype (RF-CRI) is expressed in high concentrations in the sera of some patients with rheumatoid arthritis (RA) and juvenile rheumatoid arthritis (JRA). To determine if RF-CRI is specifically expressed in rheumatic disease or if it is secondary to polyclonal B-cell activation, we examined sera of 23 children with SLE, 16 adolescents with infectious mononucleosis (IM), and age-matched pediatric controls for RF-CRI expression. Concentrations of RF-CRI in serum, determined by an inhibition ELISA, were 24 +/- 17 micrograms/ml (mean +/- SD) in 25 normal children, 31 +/- 17 in 16 young adults with IM, and were significantly increased, 70 +/- 80 micrograms/ml, in the 23 children with SLE (p less than 0.036). Eleven of 23 SLE patients had serum RF-CRI greater than the mean +/- 2 SD for normal children. Ten of 23 SLE sera contained IgM rheumatoid factor (RF) activity. One patient with IM had a borderline elevated RF-CRI level, and 5 IM patients had RF in their sera. The serum IgM concentrations in sera were: SLE (192 +/- 93 mg/dl) and IM (234 +/- 77 mg/dl) sera. These levels were significantly elevated compared to controls (132 +/- 44 mg/dl), p less than 0.031 for SLE and p less than 0.001 for IM, suggesting that polyclonal activation of B cells was present in SLE and IM patient groups. Increased expression of RF-CRI in the SLE patients correlated directly with high titer anti-DNA antibody values (r = 0.3965, p less than 0.05) and RF activity when human IgG (r = 0.5026, p less than 0.05) was used as the RF binding substrate and inversely with serum C3 levels (r = 0.3925, p less than 0.05). RF-CRI expression did not correlate with RF that bound rabbit (r = 0.3123, p greater than 0.05). Increased serum RF-CRI expression is not a result of polyclonal B-cell activation. RF-CRI may be selectively up-regulated in patients with SLE.     

Anti-cardiolipin antibodies in ischaemic heart disease.

IgG and IgM anti-cardiolipin antibodies (ACA) were assayed by an ELISA technique in 86 patients with ischaemic heart disease (IHD) and compared to 124 healthy controls and to 62 patients with rheumatoid arthritis (RA) and 20 with tuberculosis (TB). IgG ACA levels in IHD, RA and TB were comparable and significantly higher than in controls (P less than 0.0001). IgM ACA was significantly higher in IHD and RA than controls (P less than 0.0001) but not TB (P = 0.045). The number of IHD patients with raised ACA (IgG and/or IgM) was significantly greater than in RA or TB. (chi 2 = 30.77, P less than 0.0001). ACA were raised in 80.2% IHD patients on one or more occasions during a 1-11 day (mean 4.7) hospital admission. There was no difference in either ACA levels or in the frequency of ACA elevation in patients with stable or unstable angina pectoris or myocardial infarction. We conclude that there is a strong association between IHD and ACA with potentially important therapeutic implications.     

Increased spontaneous secretion of rheumatoid factor by intestinal lamina propria mononuclear cells from Crohn's disease but not ulcerative colitis patients.

Increased levels of rheumatoid factors (RF) have been observed in the serum of Crohn's disease but not ulcerative colitis patients, and have been proposed to relate to an increased state of intestinal lymphocyte activation. We have therefore examined the spontaneous in vitro secretion of RF by intestinal lamina propria mononuclear cells (MNC) isolated from specimens from control and inflammatory bowel disease (Crohn's disease, ulcerative colitis) patients. Normal intestinal lamina propria MNC spontaneously secrete rheumatoid factors of different isotypes during 14 days of in vitro culture (9.7 ng/ml IgA RF, 11.6 ng/ml IgM RF and 64.6 ng/ml IgA anti-Fc (IgG)). In matched studies intestinal MNC isolated from normal large bowel exhibited significantly greater levels of RF synthesis and secretion in vitro than normal small bowel intestinal MNC. A large increase in spontaneous RF secretion was observed from Crohn's disease intestinal MNC (21.4 ng/ml IgA RF, 21.4 ng/ml IgM RF, and 108.15 ng/ml IgA anti-Fc (IgG)), when compared with normal controls. The amount of RF secreted was dependent on the amount of inflammatory activity of the bowel specimens, from which the MNC were isolated (198.3 ng/ml of IgA anti-Fc(IgG) from involved versus 50.0 ng/ml from matched non-involved tissue). Ulcerative colitis MNC released decreased amounts of RF (7.1 ng/ml IgA RF, 6.2 ng/ml IgM RF, and 42.3 ng/ml IgA anti-Fc(IgG)). These observations using isolated intestinal MNC may explain the findings of RF changes in the sera of inflammatory bowel disease patients. Our observations support the hypothesis of a heightened state of activation in normal intestinal lamina propria MNC, which is further increased in active Crohn's disease. The dissimilarities observed between Crohn's disease and ulcerative colitis may indicate fundamental differences in disease pathophysiology and will lead to further studies exploring intestinal immunoregulatory properties of RF.