Expression of a common idiotype PR4 in the sera of patients with leprosy.

The sera of 187 patients from across the leprosy spectrum were screened for the expression of the PR4 idiotype, which was first identified on a human hybridoma-derived monoclonal antibody from a patient with leprosy and found to react with the Mycobacterium leprae phenolic glycolipid and a variety of polynucleotides. Sixty per cent (51 out of 85) of patients with lepromatous leprosy (LL), 66% (33 out of 49) with borderline lepromatous (BL) disease, 47% (14 out of 30) with borderline tuberculoid (BT) leprosy, and 56% (13 out of 23) of tuberculoid (TT) patients were found to have significantly elevated titres of the PR4 idiotype in their sera compared with endemic controls, irrespective of the presence or absence of endemic malaria. Sera from 52 patients with tuberculosis were also screened as a control for mycobacterial infection. The PR4 idiotype was significantly elevated in 37% (19 out of 52) of these patients. No correlation between idiotype and serum immunoglobulins IgG and IgM was found, indicating that the concentrations of idiotype levels in sera were not merely a reflection of changes in serum immunoglobulin levels. It is hypothesized that the expression of the PR4 idiotype is due to certain germline genes preferentially expressed rather than being the result of polyclonal B cell activation.

Specificity of lymphocytotoxic autoantibodies (LCAbs) found in the serum of leprosy patients: class I MHC antigens.

Lymphocytotoxic autoantibodies (LCAbs) of the IgM class have been identified in patients with borderline tuberculoid (BT) and borderline lepromatous (BL) leprosy with Type I reactions (I) as well as lepromatous leprosy (LL) patients with erythema nodosum leprosum reactions (ENL). The observation that lymphocytotoxic activity (LCA) was reduced in the presence of platelets led us to determine whether LCAbs had specificities for Class I Major Histocompatibility Complex (MHC) determinants. Absorption of LCA positive sera with platelets, classically used to deplete Class I specific lymphocytotoxic antibodies, reduced LCA towards autologous as well as allogeneic target cells. This was true for LCA positive sera from all patient classifications (group BT in the autologous system, p less than 0.01; in all other patient groups, p less than 0.001). Introducing B-2m to cytotoxicity assays only marginally reduced LCA when added at high concentrations (5 mg/ml). An anti-Class I MHC antiserum which blocked the lytic activity. The data indicate that LCAbs while absorbed by platelets, are not specific for the Class I MHC antigens. The autoantigen recognized by these autoantibodies therefore remains to be identified.

Serum lymphocytotoxic activity in leprosy.

Sera from 167 patients across the spectrum of leprosy and 46 endemic controls were screened for lymphocytotoxic activity (LCA). The Terasaki microdroplet lymphocytotoxicity assay was performed at 37 degrees C and 15 degrees C to test sera for LCA against a panel of lymphocytes from 50 donors which represented most known HLA-ABC antigens. Raised complement-dependent LCA at 15 degrees C was seen in leprosy patients with histories of erythema nodosum leprosum (ENL) or reversal/Type I (I) reactions. Eighty-six per cent of lepromatous (LL) patients with a history of ENL (n = 21, P less than 0.001), 83% of borderline lepromatous (BL) and 88% of borderline tuberculoid patients (BT) with a history of Type I reactions (n = 12, P less than 0.01 and n = 24, P less than 0.001 respectively) had LCA compared to 39% of endemic controls (n = 46). LCA was attributed to IgM on the basis of reduced activity when serum was treated with both dithiothreitol or absorbed with antiserum for IgM. Removal of immune complexes and rheumatoid factor did not influence LCA. LCA-positive sera reacted similarly with allogeneic lymphocytes from either healthy donors or leprosy patients. Moreover LCA-positive sera reacted with autologous lymphocytes. Specificities for HLA-ABC antigens were not identified. The potential role of these autoantibodies, manifested in leprosy patients with hypersensitivity reactions remains speculative.

Recognition of mycobacterial antigens by sera from patients with leprosy.

Mycobacterium leprae sonic extracts prepared from armadillo-derived bacteria were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting (immunoblotting) procedures and probed with serum or plasma samples from 20 patients with lepromatous leprosy and 14 healthy endemic controls. Five proteins of 33, 25, 18, 15, and 12 kilodaltons (kDa) were frequently recognized; the 33- and 15-kDa proteins were, respectively, recognized with high intensity by 16 and 13 of the 20 samples from patients with leprosy, whereas only one healthy donor had antibodies that recognized the 15-kDa protein. By the use of M. leprae-specific murine monoclonal antibodies it was demonstrated that the 33-, 25-, and 15-kDa antigens were different from those bound by the available murine monoclonal antibodies. The 18- and 12-kDa proteins detected had molecular masses similar to those detected by the corresponding murine monoclonal antibodies. The serum and plasma samples from patients with leprosy were also used to probe Western blots of a soluble extract of M. tuberculosis. They recognized, among others, antigens with molecular weights similar to those detected in the M. leprae antigenic preparations, although with less intensity and at a lower frequency.

Studies of a common idiotype PR4 in autoimmune rheumatic disease.

A new common idiotype, designated PR4, is described. This idiotype was originally identified on a human hybridoma-derived monoclonal antibody from a patient with leprosy, which binds the major Mycobacterium leprae-derived antigen, phenolic glycolipid-1, poly(ADP)-ribose, DNA, and poly(dT). The PR4 idiotype was found in patients with systemic lupus erythematosus (SLE) (70%), rheumatoid arthritis (40%), and Sjögren's syndrome (15%). It was not, however, found in the spouses of the SLE patients or (unlike other lupus idiotypes) in their healthy first-degree relatives. Although no correlation between PR4 idiotype levels and disease activity in SLE was found, a subset of rheumatoid arthritis patients with high levels of the idiotype was identified.

Human monoclonal antibodies to phenolic glycolipid-I derived from patients with leprosy, and production of specific anti-idiotypes.

Human monoclonal antibodies (mAb) were produced by hybridomas derived from fusion of the GM4672 lymphoblastoid cell line and peripheral blood mononuclear cells from leprosy patients. Hybridoma supernatants were screened for immunoglobulin (Ig) secretion, binding to Mycobacterium leprae, phenolic glycolipid-I (Phen GL-I), the unique M. leprae glycolipid and single-stranded(ss)DNA by ELISA. On the basis of direct-binding ELISAs, two IgMk mAb (PR4 and TH3) were selected for characterization. PR4 and TH3 bound to M. leprae, Phen GL-I and ssDNA; PR4 also bound to M. avium and M. kansasii and TH3 to M. kansasii. Inhibition assays demonstrated that these antibodies did not bind to the terminal disaccharide of Phen GL-I. In addition, both PR4 and TH3 bound to several autoantigens: ssDNA, double-stranded(ds)DNA and poly(ADP-ribose) but not RNA. PR4 and TH3 were used for preparation of rabbit anti-idiotype antisera. Inhibition studies demonstrated that the affinity purified rabbit anti-idiotype antisera were specific for their respective idiotype and that both Phen GL-I and ssDNA inhibited binding of idiotype to its anti-idiotype. PR4, but not TH3, was found to be similar but not identical to the 16/6 idiotype originally identified on a human monoclonal anti-DNA antibody derived from a patient with systemic lupus erythematosus (SLE).

Human monoclonal antibodies to phenolic glycolipid-1 from leprosy patients cross react with poly(ADP-ribose), polynucleotides and tissue bound antigens.

Antibodies which bind to poly(ADP-ribose) have been described in Systemic Lupus Erythematosus (SLE) and a variety of infectious diseases. Two IgM kappa human monoclonal antibodies (MAbs), TH3 and PR4, produced from the fusion of peripheral blood lymphocytes of leprosy patients with the GM4672 lymphoblastoid cell line, were found to bind to poly(ADP-ribose) in direct binding and inhibition ELISAs. Significant inhibition of binding of these MAbs to poly(ADP-ribose) occurred with phenolic glycolipid-1, the M. leprae specific glycolipid, ssDNA, dsDNA, poly(dT), as well as poly(ADP-ribose) itself. Up to 80% of binding of TH3, and 90% of binding of PR4, to poly(ADP-ribose) was inhibited by 10 mcg of ssDNA suggesting that there may be sharing of some conformational determinants. Although the serological binding profiles of TH3 and PR4 are similar, only PR4 was found to bind to basal keratinocytes of normal human interfollicular epidermis and astrocyte cytoplasm in normal brain tissue. These results support the concept that an antibody binding site may accommodate more than one epitope. Furthermore, small differences in antigen binding potential may distinguish relatively innocuous antibodies from those which may be more pathogenic.

Assessment of the immune deficit in leprosy patients and the effect of recombinant IL-2 in vitro.

Although the mechanism of immunologic unresponsiveness in lepromatous leprosy remains unknown, it has been shown that interleukin-2 (IL-2) production is defective in these patients. Peripheral blood mononuclear cells (PBMC) were isolated from treated (less than 16 months) and untreated leprosy patients as well as household contacts; age, sex, ethnically matched control subjects; and laboratory staff. PBMC were cultured for 6 days with sonicated Mycobacterium leprae (1-10 micrograms/ml), Dharmendra lepromin (1:10), or phenolic glycolipid-I (PGL-I) (0.05-5.0 micrograms/ml) in medium supplemented with various concentrations of recombinant IL-2 (rIL-2) or cultured for 3 days with one of the three mycobacterial antigens in the presence of concanavalin A (ConA). TT/BT patients and household control subjects had a robust response to M. leprae and lepromin, but were unresponsive to PGL-I delivered in liposomes. PBMC from LL patients did not respond to any of the three antigen preparations. rIL-2 induced proliferation of PBMC both in leprosy patients and control subjects regardless of the presence or absence of the three leprosy antigen preparations. This antigen nonspecific augmentation of proliferation by the wide range of doses of rIL-2 employed makes difficult the interpretation of the enhanced thymidine incorporation noted when rIL-2 is added in the presence of antigen to cultures of lymphocytes from LL patients. Our studies are at variance with reports that leprosy antigens, specifically PGL-I, induce immunological suppression, in that mycobacterial antigens did not cause significant suppression of the ConA-induced proliferations of PBMC from patients.