Complement regulators in human disease: lessons from modern genetics.

First identified in human serum in the late 19th century as a 'complement' to antibodies in mediating bacterial lysis, the complement system emerged more than a billion years ago probably as the first humoral immune system. The contemporary complement system consists of nearly 60 proteins in three activation pathways (classical, alternative and lectin) and a terminal cytolytic pathway common to all. Modern molecular biology and genetics have not only led to further elucidation of the structure of complement system components, but have also revealed function-altering rare variants and common polymorphisms, particularly in regulators of the alternative pathway, that predispose to human disease by creating 'hyperinflammatory complement phenotypes'. To treat these 'complementopathies', a monoclonal antibody against the initiator of the membrane attack complex, C5, has received approval for use. Additional therapeutic reagents are on the horizon.

Hyperphosphorylation of autoantigenic targets of paraproteins is due to inactivation of PP2A.

Paratarg-7, a frequent autoantigenic target, and all other autoantigenic targets of human paraproteins molecularly defined to date are hyperphosphorylated in the respective patients compared with healthy controls, suggesting that hyperphosphorylation of autoantigenic paraprotein targets is a general mechanism underlying the pathogenesis of these paraproteins. We now show that hyperphosphorylation of paratarg-7 occurs because of an additional phosphorylation of Ser17, which is located within the paraprotein-binding epitope. Coimmunoprecipitation identified phosphokinase C ζ (PKCζ) as the kinase responsible for the phosphorylation of most, and phosphatase 2A (PP2A) as the phosphatase responsible for the dephosphorylation of all hyperphosphorylated autoantigenic targets of paraproteins. Single-nucleotide polymorphisms (SNPs) or mutations of PKCζ and PP2A were excluded. However, PP2A was inactivated by phosphorylation of its catalytic subunit at Y307. Stimulation of T cells from healthy carriers of wild-type paratarg-7 induced a partial and transient hyperphosphorylation between days 4 and 18, which was maintained by incubation with inhibitors of PP2A, again indicating that an inactivation of PP2A is responsible for the hyperphosphorylation of autoantigenic paraprotein targets. We conclude that the genetic defect underlying the dominantly inherited hyperphosphorylation of autoantigenic paraprotein targets is not in the PP2A itself, but in genes or proteins controlling PP2A activity by phosphorylation of its catalytic subunit.

Cytoplasmic cytokines in lymphoproliferative disorders: multiple cytokine production in angioimmunoblastic lymphadenopathy with dysproteinemia.

Cytokines play an important role in the pathogenesis of lymphomas via autocrine or paracrine mechanisms, or both. Here we determined the proportion of CD3-positive T lymphocytes containing various types of cytokines in enlarged lymph nodes. Lymph nodes were obtained from 16 patients with various lymphoproliferative disorders, including 3 cases with angioimmunoblastic lymphadenopathy with dysproteinemia (AILD), 3 cases with adult T cell leukemia/lymphoma (ATLL), 2 cases with T-cell nonspecific malignant lymphoma (T-ML), 3 cases with B-cell diffuse large malignant lymphoma (BDL), 3 cases with histiocytic necrotizing lymphadenitis (HNL), and 2 cases with non-specific lymphadenitis (NSL). The percentages of T lymphocytes positive for cytoplasmic cytokines IL-2, IL-4, IL-5, IL-6, IL-13, TNF-alpha, and INF-gamma were determined. The percentage of INF-gamma positive T lymphocytes was high in reactive lymphadenopathy of NSL and HNL. AILD showed a high proportion of TNF-alpha positive T-lymphocytes, and in addition, the percentages of IL-2, IL-4, IL-5, IL-6, IL-13 and INF-gamma positive T-lymphocytes were relatively higher than in other diseases. Our results supported the state of multiple hypercytokinemia typically seen in AILD and suggested that the source of the cytokines is the lymph nodes. Our results also suggested that multiple cytokine networks play an important role in the clinical and histopathological features of AILD. Modulation of the cytokine network may be the logical objective in future therapeutic strategies designed for AILD.

Immunoglobulin VH gene sequence analysis of spontaneous murine immunoglobulin-secreting B-cell tumours with clinical features of human disease.

The 5T series of multiple myelomas (MM) and Waldenstrsöm's macroglobulinaemia-like lymphomas (WM), which developed spontaneously in ageing mice of the C57BL/KaLwRij strain, shows clinical and biological features that closely resemble their corresponding human diseases. In order to compare the patterns of somatic mutation in VH genes of mouse tumours with those of human counterparts, we have determined and analysed sequences of immunoglobulin VH genes in five cases of murine MM, two of WM and one of biclonal benign monoclonal gammopathy (BMG). Four of five MM and 2/2 WM cases used VH genes of the large J558 family; one MM used a gene of the VGAM3.8 family, and both clones of the BMG used genes of the 36-60 family. N-region insertions were observed in all cases, but D-segment genes were only identified in 6/9 cases, which were all from the D-SP family and translated in reading frame 3. Compared with human MM, in which the VH genes have been found to be consistently hypermutated (mean% +/- SD = 8.8 +/- 3.2), the degree of somatic mutation in the murine tumours was significantly lower (mean% +/- SD = 2.9 +/- 2.3). There was no significant evidence of clustering of replacement mutations in complementarity determining regions (CDR), a feature considered to be characteristic of antigen-selected sequences. However, one clone of the biclonal BMG case showed intraclonal variation, a feature described in some cases of human BMG. These results indicate that murine VH genes in mature tumours differ from human counterparts in the level and distribution of somatic mutations, but support the concept that BMG may be distinct from MM.

Dys- and paraproteinaemias in patients suffering from ophthalmic herpes zoster.

Humoral immune parameters were measured in 93 patients suffering from ophthalmic herpes zoster. The control group consisted of 31 other ophthalmic patients. In all cases, electrophoresis, immunoglobulins, acutephase proteins, immune complexes, antinuclear antibody and complement components were determined as well. In patients suffering from ophthalmic herpes zoster the main immunological deviations among the humoral parameters were found in the non-specific immune response. These alterations were comparable with the extent and severity of the pathological processes. Para-proteins were detected in 12% of the patients. In contrast they were not present in the control group.

NIH conference. Angioimmunoblastic lymphadenopathy with dysproteinemia.

Angioimmunoblastic lymphadenopathy with dysproteinemia is a disorder characterized by a sudden onset of constitutional symptoms and lymphadenopathy. Patients often have hypergammaglobulinemia, autoantibodies, rashes, thrombocytopenia, or hemolytic anemia. Diagnosis requires a lymph node biopsy that shows architectural effacement, absence of germinal centers, arborization of postcapillary venules, and a polymorphous infiltrate that includes immunoblasts. Early in the disease, activated T cells in blood and lymph nodes stimulate B cells to proliferate and produce antibody. However, late in the disease, immune suppression may result from increased suppressor function. Clonal rearrangements, which are seen in all patients with regard to either the T-cell receptor beta-chain gene or immunoglobulin genes, have been followed by malignant transformation and frank lymphoma in some patients. Thus, this disorder stands partway between benign lymphoid proliferation and clonal lymphoid transformation. The prognosis of this disorder is poor; 75% of patients die within 2 years or develop a lymphoid malignancy. The rest usually go into a sustained remission. Current treatment with corticosteroid and immunosuppressive agents is unsatisfactory, especially because of late immunosuppression and predisposition to infections.

Flow cytometric measurement of antiplatelet antibodies.

A flow cytometric technic was developed to detect platelet surface-bound immunoglobulin in patients with thrombocytopenia. Elevated platelet surface IgG and/or IgM was detected in 90.9% of patients with immune thrombocytopenia purpura (ITP). False positive results occurred in 9.3% of patients with nonimmune thrombocytopenia usually associated with sepsis. False negatives occurred most frequently in adults with chronic ITP. Measurement of platelet surface immunoglobulin with this flow cytometric technic helps differentiate immune from nonimmune thrombocytopenia.

[Noncompressive myelopathy and dysglobulinemia. A fortuitous association? Discussion of 3 new cases]. / Myélopathies non compressives et dysglobulinémies. Association fortuite? Discussion de trois nouveaux cas.

Three new cases of myelopathy without compression associated with paraproteinemia are reported. The neurologic picture was that of spinal muscular atrophy in one case and chronic spinal combined sclerosis in two. The nature of the paraproteinemia is discussed: all three patients seem to have had benign monoclonal dysglobulinemia. One patient died from cardiovascular disease five years after onset, and another from complications related to decubitus seven years after onset. Postmortem examination was not possible in either case. Spinal muscular atrophy has been reported in certain carcinomas (lung, stomach, breast) and, less frequently, in macroglobulinemia. As benign dysglobulinemia is common after sixty, coincidental association cannot be outruled. However, data from the literature and the response to cancer chemotherapy in two patients suggest an original pathologic association. Recent demonstration of demyelinating neuropathies associated with benign paraproteinemia provide further evidence in support of such an association.

Interaction of plasma fibronectin with selected cryoglobulins.

Plasma fibronectin (PFN) is associated with cryoglobulins of the polyclonal type. Cryoglobulins from two patients with essential mixed cryoglobulinaemia were analysed immunoelectrophoretically to determine a possible association between PFN and immunoglobulin complexes in the formation of cryoprecipitates. In cryoglobulins from each patient, distinctive alterations in electrophoretic migration patterns of both PFN and immunoglobulin were associated with the formation of a cryoprecipitate. The observations indicate that PFN binds to some serum component in the process of cryoglobulin formation. That component may be immunoglobulin.

[Circulating immunocomplexes in patients with various morbid conditions]. / Immunocomplessi circolanti in pazienti con varie condizioni morbose.

The polyethylenglycol (PEG) precipitation technique has been employed for the measurement of immune complexes in the circulation of 100 normal subjects and in 14 patients suffering from a variety of diseases (systemic lupus erythematodes, nephrosic syndrome, cryoglobulinaemia, Buckley's syndrome). Values higher than 0.80 UA on the absorption scale were considered pathological, namely 2 standard deviations above the mean (0.32 UA) in the subjects examined; in the patients, values between a minimum of 0.98 UA and a maximum of 2.38 UA were observed. Longitudinal study of these cases also pointed to the disappearance of immune complexes during therapy. The results suggest that the PEG precipitation technique can play an important part as a screening test in situations in which circulating IC pathology is suspected; it is also a sensitive means of monitoring treatment.

The association of cryoglobulinaemia with nodules, vasculitis and fibrosing alveolitis in rheumatoid arthritis and their relationship to serum C1q binding activity and rheumatoid factor.

Two measurements of serum immune complexes, cryoglobulinaemia and 125I-C1q binding, have been performed in patients with severe rheumatoid arthritis (RA) and compared with normal levels. Cryoglobulinaemia was present in 20 out of 28 patients (71%) with extra-articular disease (mean level 17 micrograms/ml) including nodules, digital vasculitis, cutaneous ulcers, rash, neuropathy, lung disease and scleritis, but in none of 32 patients with joint disease alone (uncomplicated RA) (mean level 3 micrograms/ml). Cryoglobulinaemia correlates with, but probably does not antedate, extra-articular disease, and may be useful in predicting morbidity and mortailty in this group of patients. In contrast, serum 125I-Clq binding was raised in patients with uncomplicated RA and those with extra-articular disease, although levels were higher in the latter group. Both tests showed a negative correlation with serum haemolytic complement and a positive correlation with IgM rheumatoid factor although there were some sera with raised levels of rheumatoid factor without cryoglobulinaemia. These results suggest that cryoglobulinaemia is a better test than Clq-binding for demonstrating the presence of circulating immune complexes involved in the pathogenesis of extra-articular lesions.