Significance of aPL IgG subclasses

Autoantibodies in SLE: Specificities, Isotypes and Receptors

Systemic Lupus Erythematosus (SLE) is characterized by a wide spectrum of auto-antibodies which recognize several cellular components. The production of these self-reactive antibodies fluctuates during the course of the disease and the involvement of different antibody-secreting cell populations are considered highly relevant for the disease pathogenesis. These cells are developed and stimulated through different ways leading to the secretion of a variety of isotypes, affinities and idiotypes. Each of them has a particular mechanism of action binding to a specific antigen and recognized by distinct receptors. The effector responses triggered lead to a chronic tissue inflammation. DsDNA autoantibodies are the most studied as well as the first in being characterized for its pathogenic role in Lupus nephritis. However, others are of growing interest since they have been associated with other organ-specific damage, such as anti-NMDAR antibodies in neuropsychiatric clinical manifestations or anti-β2GP1 antibodies in vascular symptomatology. In this review, we describe the different auto-antibodies reported to be involved in SLE. How autoantibody isotypes and affinity-binding to their antigen might result in different pathogenic responses is also discussed.

Cryoglobulinemia in chronic hemodialysis patients

BACKGROUND

Renal failure patients submitted to chronic hemodialysis can present with cryoglobulinemia. There are few studies on cryoglobulins in chronic hemodialysis patients. The aim of the present study was to determine the prevalence and to identify the components of cryoglobulins in chronic hemodialysis patients.

METHODS

Fifty-four patients on chronic hemodialysis were evaluated for the presence of cryoglobulins, after inclusion and exclusion criteria. The components of the cryoprecipitate were analyzed.

RESULTS

Cryoglobulins were detected in 83% (45/54) of the patients on chronic hemodialysis. The cryoprecipitate was constituted by IgG, IgM, IgA, and complement fractions C3 and C4.

CONCLUSION

We concluded that there was a high prevalence of cryoglobulins in chronic hemodialysis patients, and the cryoprecipitate was constituted by IgG, IgM, IgA, and complement fractions C3 and C4.

Current insight into diagnostics and pathophysiology of the antiphospolipid syndrome

The diagnosis of the antiphospholipid syndrome, a non-inflammatory autoimmune disease characterized by thrombosis or pregnancy morbidity in the presence of antiphospholipid antibodies, depends greatly upon laboratory diagnostics. The diagnostic value of all available assays to detect antiphospholipid antibodies and the anticardiolipin assay in particular, is a matter of ongoing debate. Although the presence of lupus anticoagulant correlates best with thrombosis, accurate determination is not always possible due to anticoagulant treatment. Data on the predictive value of alternatives such as the anti-beta2-glycoprotein I and the anti-prothrombin antibody assay are insufficient and prospective cohort studies are needed. Determining antiphospholipid antibody profiles seems to increase diagnostic specificity. Substantial progress has been made in unravelling the pathophysiological mechanisms underlying the antiphospholipid syndrome. Several cellular receptors for antibody-beta2-glycoprotein I complexes have been identified and their roles in cellular activation are being investigated. In vivo data should provide more insight into the importance of the interaction with individual receptors.

Antiphospholipid antibodies in ocular arterial and venous occlusive disease

PURPOSE

It was the aim of this study to evaluate antiphospholipid antibodies (APA), i.e. lupus anticoagulants (LA) and anticardiolipin (ACA) IgG and IgM, in ophthalmic occlusive disease.

METHODS

Over a 3.5-year period, APA were evaluated in 368 patients.

RESULTS

Eighty-six patients (23.4%), compared to 5% in the general population, tested positive for APA. APA did not differ significantly between patients with venous (20.6%) or arterial (25.5%) occlusive disease. This included 93 patients with central retinal vein occlusion (18% APA positive), 67 with retinal branch vein occlusion (24% APA positive), 41 with central retinal artery occlusion (22% APA positive), 53 with retinal branch artery occlusion (32% APA positive), 71 with anterior ischemic optic neuropathy (23% APA positive), 12 with posterior ischemic optic neuropathy (33% APA positive) and 31 patients with amaurosis fugax (23% APA positive). Excluding patients with accepted main risk factors, APA were positive in 15.3% of 85 patients.

CONCLUSION

The high APA prevalence confirms its relevance in ocular occlusive disorders.

Primary anti-phospholipid antibody syndrome (APS): current concepts

Primary anti-phospholipid syndrome (APS) is a thrombophilic state characterized by recurrent arterial and venous thrombosis, recurrent pregnancy loss, and the presence of circulating anti-phospholipid antibodies that may be responsible for thrombophilia and pregnancy morbidity. Ophthalmologic features are present in 15-88% of the patients with primary APS, thus ophthalmologists are one of the first physicians to whom the patient will present. An accurate diagnosis may save the patient from recurrent, potentially life-threatening thrombosis. In the U.S.A., an estimated 35,000 new cases of APS-related venous thrombosis occur each year in a population that is several decades younger than the patient population typically affected by thrombosis. Clinical features, such as chorea, transverse myelitis, cardiac valvular lesions, and accelerated atherosclerosis, are hypothesized to be due to a direct tissue-antibody interaction and cannot be explained purely by thrombosis. The use of recently proposed, well-defined diagnostic criteria, and better standardization of laboratory assays for the anti-phospholipid antibodies should help enable epidemiological surveys to establish the prevalence of these antibodies in patients with thrombosis and in the general population. Diagnosis of APS should be considered in all patients with recurrent systemic or ocular thrombosis in the absence of known risk factors. Several well-designed prospective studies show an increased risk of thrombosis in the presence of medium to high antibody level. With ocular involvement in as many as 88% of APS patients, an ophthalmic assessment should be an integral part of the clinical work-up of any patient with suspected or confirmed APS. The presence of isolated ocular thrombophilia with persistently elevated anti-phospholipid antibodies or lupus coagulant should confirm the diagnosis of APS. Management of these patients must be a multi-disciplinary effort with either a rheumatologist or a hematologist having the overall responsibility for coordinating treatment and monitoring the patient's immune status and anticoagulation. Treatment of isolated ocular thrombophilia in the presence of moderate to high titers of antiphospholipid antibodies should be on the same principles as patients with APS to prevent recurrent ocular or cerebral thrombosis.

Alterations of cerebral blood flow and antiphospholipid antibodies in patients with systemic lupus erythematosus

Twenty-two patients with systemic lupus erythematosus and 13 healthy controls were included in a cerebral blood flow study and underwent brain-dedicated single-photon emission computed tomography using 99m technetium-d, l-hexamethylpropylene amine oxime together with a brain computed tomography scan. Plasma levels of antiphospholipid antibodies (lupus anticoagulant and anticardiolipin IgM and IgG antibodies) were also determined. Brain computed tomography showed signs of focal cerebral ischemia in 4 patients (18%), whereas cerebral blood flow by single-photon emission computed tomography was abnormal in 13 of 22 patients (59%), who showed bilateral or monolateral hypoperfusion in the temporo-parietal regions. Patients with abnormal cerebral blood flow had a longer duration of disease than those with normal blood flow (8.9 +/- 1.9 years vs. 5.3 +/- 1.5 years, P < 0.05). Plasma antiphospholipid antibodies were present in 15 patients (68%), but the prevalence was similar in those with normal (6/9, 66%), or abnormal (9/13, 69%) cerebral blood flow. No statistically significant difference in lupus anticoagulant or anticardiolipin antibodies was observed between patients with and without cerebral blood flow abnormalities. Our study shows that patients with systemic lupus erythematosus frequently have cerebral blood flow abnormalities, which could precede those observed by computed tomography. Plasma lupus anticoagulant and anticardiolipin titers were not correlated with normal cerebral blood flow.

IgG anticardiolipin antibody titer > 40 GPL and the risk of subsequent thrombo-occlusive events and death. A prospective cohort study

BACKGROUND

Anticardiolipin antibodies (aCL) have been associated with an increased risk of stroke and thrombo-occlusive events. Little is known about the influence of aCL on recurrent thrombo-occlusive events.

METHODS

Consecutively identified patients (n = 132) with focal cerebral ischemia [stroke = 112, transient ischemic attack (TIA) = 20] harboring aCL of at least 10 GPL units at the time of their index event were prospectively followed to estimate the effect of aCL titer on time to and risk of subsequent thrombo-occlusive events (stroke, TIA, deep venous thrombosis, pulmonary embolism, myocardial infarction) and death. On the basis of prior literature, we divided patients into those with aCL < or = 40 GPL (n = 111; mean age, 63 +/- 14 years; mean follow-up, 1.95 years) and those with aCL > 40 GPL (n = 21; mean age, 54 +/- 20 years; mean follow-up, 1.50 years).

RESULTS

There was no difference between groups for prevalence of hypertension, diabetes mellitus, cigarette smoking, atrial fibrillation, prior TIA, or sex. The GPL > 40 group was younger (54 +/- 20 versus 63 +/- 14 years; P = .055), had more prior strokes [9/21 (48%) versus 27/111 (20%); P = .030], more frequent subsequent thrombo-occlusive events and death [15/21 (71%) versus 51/111 (48%); P = .030], and a shorter median time (years) to event (0.15 versus 0.61, log rank P = .005). The risk ratio for recurrent event and death with GPL > 40 obtained from Cox proportional hazards models, adjusted for prior strokes, prior TIAs, hypertension, diabetes mellitus, atrial fibrillation, and cigarette smoking was 1.9 (95% confidence interval, 1.0 to 3.5; P = .051).

CONCLUSIONS

Our data suggest that subsequent thrombo-occlusive events and death after focal cerebral ischemia associated with IgG aCL may occur sooner and more frequently with GPL > 40.