Urinary excretion of CD23 antigen in normal individuals and patients with chronic lymphocytic leukaemia (CLL)

Origin and properties of soluble CD21 (CR2) in human blood

By analysis with a panel of CD21 MoAbs it is shown that a large part of the soluble CD21 in human blood plasma is of the long isoform (CD21L), as judged by comparison with antigen produced by mouse L cells transfected with CD21L-cDNA and reactivity with the restricted CD21 MoAb R4/23. This is compatible with the hypothesis that soluble CD21 in the blood is mainly derived from follicular dendritic cells (FDC). Cells from a human keratinocyte cell line transfected with cDNA from the Burkitt lymphoma cell line Raji also produced soluble CD21L (sCD21L), whereas the short form of sCD21 (sCD21S) was the major component of sCD21 produced by the B lymphoblastoid cell line LICR-LON-HMy and the T cell line Jurkat. Confocal studies of FDC isolated from human tonsil revealed that CD21 was present in the cytoplasm. On gel filtration sCD21 from untreated serum has an apparent size considerably greater than the 130kD found by SDS-PAGE analysis. This may be partly accounted for by the non-globular shape of the molecule, but may also indicate, as reported by others, that in its native state sCD21 is complexed with other proteins. However, no evidence of complexing with sCD23 or C3d could be found.

Evaluation of soluble IL-6 receptor concentration in serum and epithelial lining fluid from patients with interstitial lung diseases

We measured soluble IL-6 receptor (sIL-6R) levels in serum and bronchoalveolar lavage fluids (BALF) from patients with interstitial pneumonia of unknown etiology (IP) (n = 17), sarcoidosis (n = 8) and normal control subjects (n = 10), to investigate its role in pulmonary diseases. Soluble IL-6R was determined by an ELISA. The volume of epithelial lining fluid (ELF) in BALF was estimated using an urea method. We found that levels of sIL-6R in serum, BALF, and ELF from patients with IP or sarcoidosis were significantly higher than those from normal subjects. Furthermore, levels of sIL-6R in BALF or ELF were significantly correlated with those of albumin, indicating that sIL-6R, together with albumin, may enter ELF as a result of the increased permeability caused by pulmonary inflammation. Thus most of the sIL-6R in ELF would be from serum, and relatively small amounts of it might be produced locally. However, sIL-6R levels in ELF, but neither serum nor BALF, were significantly correlated with levels of C-reactive protein in patients with IP. These results suggest that both systemic and local production of sIL-6R are increased, and raised sIL-6R is involved in the modulation of systemic and local inflammatory responses in patients with IP and sarcoidosis.

Presence of activated eosinophils, high IgE and sCD23 titers in gingival crevicular fluid of patients with adult periodontitis

Our previous studies showed that the expression of CD23 on polymorphonuclear leukocytes (PMNLs) in gingival crevicular fluid (GCF) from adult periodontitis (AP) patients was higher than in autologous peripheral blood (PB). Percentages of eosinophils in GCF PMNLs ranged between 6 and 14%. The purpose of the present studies was to increase understanding of the potential role of eosinophils and their products, including CD23, in periodontal disease. We analysed the eosinophil fraction in GCF and PB by flow cytometry using monoclonal antibodies to CD23b (BB10), eosinophil cationic protein (ECP) in stored and secretory forms (EG1 and EG2), and CD67 (80H3). Simultaneously, we measured IgE and soluble CD23 titer and GCF and serum by ELISA. Flow cytometric analysis of BB10, EG2 and 80H3 binding showed that GCF eosinophils from AP were activated. A large BB10+ EG2+ cellular fraction was detected in GCF from AP whereas it was very low in autologous serum (9.30 +/- 2.460 vs 0.16 +/- 0.10, p < 0.001). GCF from gingivitis patients exhibited no flow cytometric evidence for the presence of BB10+ EG2+ cells. BB10+ EG1+ cells, or inactivated eosinophils rated lower in GCF than in PB both in gingivitis and periodontitis patients (0.45 +/- 0.63 vs 1.83 +/- 0.96 and 0.15 +/- 0.30 vs 1.30 +/- 0.20, p < 0.05, respectively). IgE titer in AP patients reached 1208.1 +/- 421.2 IU/ml in GCF while only 49.1 +/- 50.4 in sera. Soluble CD23 in GCF reached 236.1 +/- 81.3 ng/ml in GCF and 5.6 +/- 1.8 ng/ml in sera. GCF of gingivitis patients, however, contained no detectable sCD23.(ABSTRACT TRUNCATED AT 250 WORDS)

Synergy test for recognition of epitopes on soluble proteins; its application in the study of CD21 and CD23 antigens and their respective antibodies

Antigens such as CD21 and CD23, which express only one copy of an epitope require two monoclonal antibodies (mAbs) for their detection and estimation. This requirement is exploited in two ways in a technique based on the chromic chloride haemagglutination test. For simple titration of antigen two portions of red cells each coated with one of a pair of synergising mAbs are used in a 1:1 combination. For testing the antigenic specificity of a mAb and assessing its region of epitope binding, the mAb under test is serially diluted in fluid containing a standard amount of antigen and red cells are added to which have been attached a different mAb. If the red cell-bound mAb recognises a determinant topographically distinct from that of the soluble mAb, red cell agglutination to high titre occurs. In titrations of ascitic fluid containing approximately 1 mg/ml mAb, titres of log2(9) to log2(16) were recorded from a starting dilution of 1 in 200. Hence the test is very sensitive and only minute amounts of a mAb are required for testing. The same test system can be used for assessing the relative display of epitopes on antigen obtained from different sources, e.g., culture supernates and body fluids. The method is of general applicability to monomeric antigens and its use is illustrated by analysis of CD21 and CD23 antigens and antibodies.

Increased production of soluble CD23 in rheumatoid arthritis, and its regulation by interleukin-4

OBJECTIVE

To assess CD23 status in rheumatoid arthritis (RA) patients, as defined by the levels of CD23 expression on peripheral blood mononuclear cells (PBMC), the levels of soluble CD23 (sCD23) in sera, and the production of sCD23 by PBMC cultures and its regulation by interleukin-4 (IL-4).

METHODS

CD23 expression as determined by double fluorescence-activated cell sorter analysis and sCD23 production as determined by immunoradiometric assay were investigated in 24 RA patients and 21 controls. Soluble CD23 was measured in sera and supernatants of PBMC, activated with polyclonal activators (pokeweed mitogen [PWM] or Staphylococcus aureus Cowan strain 1, [SAC]) used either alone or in combination with IL-2 or IL-4.

RESULTS

The percentage of B cells expressing CD23 and serum levels of sCD23 were increased in patients with RA. IL-4 was a potent inducer of sCD23 production in supernatants, whereas IL-2 was inactive. Costimulation with SAC or PWM did not increase the effect obtained with IL-4 alone. When sCD23 levels in RA and control supernatants were compared, spontaneous production was found to be increased in RA PBMC: This difference from control values was even more pronounced when sCD23 levels in PBMC and purified B cells in response to IL-4, either alone or in combination with SAC or PWM, were tested. In the same supernatants, the increased secretion of sCD23 induced by IL-4 was associated with an inhibitory effect of IL-4 on Ig production, a phenomenon that was more pronounced in RA PBMC than in controls.

CONCLUSION

CD23 status in RA is characterized by increased expression of CD23 on B cells, increased production of sCD23 in sera and supernatants, and increased sensitivity of RA PBMC and B cells to IL-4.