Direct antiglobulin (Coombs) reactions in patients with connective tissue diseases

A Study of Clinical and Serological Correlation of Positive Direct Antiglobulin Test in Blood Bank at a Tertiary Care Center

Objectives  Detection of red cell bound immunoglobulins and/or complement by direct antiglobulin test (DAT) is a crucial serological assay in the diagnosis of autoimmune hemolytic anemia (AIHA). However, DAT may be positive in a variety of clinical conditions with or without hemolysis. We aimed at evaluating the clinical and serological correlation of positive DAT by categorizing the clinical conditions associated with positive DAT, estimating the presence of in vivo hemolysis in case of positive DAT with polyspecific and monospecific antisera and correlating the strength of positive DAT with the presence of hemolysis.

Materials and Methods  The prospective observational study was performed on 200 samples that were positive for DAT with polyspecific antiglobulin reagent as the baseline investigation. These samples were further tested with anti-immunoglobulin G and anti-C3 monospecific DAT reagents to evaluate the type of protein responsible for positive DAT. The antiglobulin tests were performed by tube technique. DAT positivity was graded (1+ to 4 + ) in each patient. Autocontrol test was included. The patients with positive polyspecific DAT were categorized into different clinical conditions. The presence or absence of in vivo hemolysis was evaluated in all clinical categories and also for each grade of positivity with polyspecific and monospecific antiglobulin reagents.

Statistical Analysis  Binomial logistic regression and Mann–Whitney U test were applied to between the group analyses. For categorical variables, Fisher's exact test and relative risk were used. The qualitative data were expressed in numbers and percentages.

Results  The highest number of patients (75/200, 37.5%) belonged to the autoimmune diseases group. Tuberculosis and hepatitis C were the main infectious diseases associated with positive DAT. Out of 200 DAT-positive patients, 98 (49%) had in vivo hemolysis and 102 (51%) did not have hemolysis. AIHA (22) and systemic lupus erythematosus (18) were the commonest clinical conditions associated with in vivo hemolysis. All the 11 samples that showed positivity with only anti-C3 reagent did not show any hemolysis. There was statistically significant increase in the incidence of in vivo hemolysis with increasing grades of DAT positivity with all the three antihuman globulin reagents.

Conclusion  There are different disease conditions which show positive DAT with or without hemolysis. So, it is important to clinically and serologically correlate positive DAT results.

Systemic lupus erythematosus serum deposits C4d on red blood cells, decreases red blood cell membrane deformability, and promotes nitric oxide production

OBJECTIVE

Systemic lupus erythematosus (SLE) is characterized by intravascular activation of the complement system and deposition of complement fragments (C3 and C4) on plasma membranes of circulating cells, including red blood cells (RBCs). The aim of this study was to address whether this process affects the biophysical properties of RBCs.

METHODS

Serum and RBCs were isolated from patients with SLE and healthy controls. RBCs from healthy universal donors (type O, Rh negative) were incubated with SLE or control serum. We used flow cytometry to assess complement fragment deposition on RBCs. RBC membrane deformability was measured using 2-dimensional microchannel arrays. Protein phosphorylation levels were quantified by Western blotting.

RESULTS

Incubation of healthy universal donor RBCs with sera from patients with SLE, but not with control sera, led to deposition of C4d fragments on the RBCs. Complement-decorated RBCs exhibited significant decreases in both membrane deformability and flickering. Sera from SLE patients triggered a transitory Ca(++) influx in RBCs that was associated with decreased phosphorylation of β-spectrin and with increased phosphorylation of band 3, two key proteins of RBC cytoskeleton. Finally, incubation with SLE sera led to the production of nitric oxide by RBCs, whereas this did not occur with control sera.

CONCLUSION

Our data suggest that complement activation in patients with SLE leads to calcium-dependent cytosketeletal changes in RBCs that render them less deformable, probably impairing their flow through capillaries. This phenomenon may negatively affect the delivery of oxygen to the tissues.

A potential role for microbial superantigens in the pathogenesis of systemic autoimmune disease

We have attempted herein to demonstrate how microbial superantigens could promote an abnormal form of "cognate" T helper-B cell interaction, analogous to that which may occur during GVH disease, leading to B cell activation and systemic autoimmunity. In vitro studies performed at our laboratory and others have demonstrated that resting human B cells bind microbial superantigens and present them to superantigen-reactive autologous T helper cells, resulting in T cell activation and polyclonal IgM and IgG production by the superantigen-bearing B cells. In vitro studies of microbial superantigen-mediated murine T helper-B cell interactions demonstrate preferential help for B cells that have encountered specific antigen. Both in humans and in mice, the cellular interactions involved and the B cell responses induced are highly analogous to those mediated by allospecific T helper-B cell interaction. Finally, the results of studies carried out on T cell-deficient (nude) mice suggest that microbial superantigens may trigger similar T helper cell-dependent polyclonal IgM and IgG responses in vivo. These mice will be studied over time and tested for the development of autoantibodies characteristic of SLE and of autoimmune organ system damage, the occurrence of which are predicted by our model.

Significance of multiple types of antibodies on red blood cells of patients with positive direct antiglobulin test: a study of monospecific antiglobulin reactions in 85 patients

Blood samples from 85 patients with a positive direct antiglobulin test were tested with monospecific antiglobulin reagents: anti-IgG, anti-IgM, anti-IgA, and anti-C3. No typical pattern of antiglobulin reaction could be correlated with specific diseases except for the patients with methyldopa-induced positive direct antiglobulin test, all of whom had only IgG on their red blood cells. The presence of more than 1 type of antibody on red blood cells was associated with severe haemolysis. These patients responded less frequently to steroids, and in most of them no underlying disease could be found. Most patients with complement alone on red blood cells had no evidence of haemolysis, and when present it was never severe.

Polyclonal B cell activation in the acute phase of systemic lupus erythematosus--aspects of pathogenic significance

B lymphocytes from patients suffering from systemic lupus erythematosus show increasing rates of spontaneous transformation in prolonged cultivation (144 hr). An additional B cell stimulation could be detected following the addition of sera from lupus erythematosus patients (isolated during the acute phase of disease) to the culture medium. In addition enriched mitogenic serum components from lupus sera increase the 3H-thymidine uptake of Brucella abortus primed B cells of healthy controls. The incorporation of 3H-thymidine with respect to the Brucella antigen concentration is described.

Lupus erythematosus

Lupus erythematosus (LE) is a multisystem disease. Genetic predisposition, altered immunity, hormones, drugs, viruses, and ultraviolet light all may play a role in etiology. A wide range of cutaneous lesions occur, and variants such as subacute cutaneous LE, complement-deficient LE, and neonatal LE have recently been emphasized. Management of the LE patient, including appropriate diagnostic studies and therapy relevant to the dermatologist, is discussed in the review.

Increased immune response in the acute phase of systemic lupus erythematosus and psoriatic arthritis caused by serum factors

In the acute phase of systemic lupus erythematosus the serum contains factors, with molecular weights ranging from 780,000 daltons to 1.5 million daltons, which induce blast transformation of autologous lymphocytes. In addition to the high-molecular weight components, low-molecular weight factors (75,000 and 160,000 daltons) which also induce an increase in lymphocytic transformation have also been demonstrated. In contrast to the high-molecular weight components the low-molecular factors stimulate the transformation of autologous and homologous lymphocytes. During transformation, lysis of autologous target fibroblasts occurs. The low-molecular weight mitogenic components remain stable after 30 min at 56 degrees C. The significance of such mediators for the pathogenesis of systemic lupus erythematosus is discussed.

The detection of cell-bound antibody on complement-coated human red cells

This study sought to elucidate the mechanism by which human red cells, in a variety of clinical settings, become coated in vivo with autologous complement components in the absence of anti-red cell autoantibodies demonstrable by standard methods. By means of a newly developed complement-fixing antibody consumption test, previously undetectable red cell-bound gammaG globulin could be detected and quantified. By this technique, the complement-coated red cells of 13 of 16 patients were shown to carry abnormally high numbers of gammaG molecules per cell, which were nevertheless below the level for detection by the direct antiglobulin test. Eluates were made from the red cells of seven of these patients and each eluate, when sufficiently concentrated, was capable of sensitizing normal human red cells (with gammaG antibodies) to give a positive indirect antiglobulin test with anti-gammaG serum. In the presence of fresh normal serum, six of the eluates so tested were capable of fixing complement to normal human red cells. The antibodies in the red cell eluates did not exhibit Rh specificity and did not react with nonprimate red cells. When studied by sucrose gradient ultracentrifugation, the gammaG antibodies to human red cells in these eluates sedimented in the 7S region. It is concluded that in many patients in whom direct antiglobulin tests reveal only cell-bound complement, the complement fixation is mediated in vivo by small quantities of "warm-reacting" erythrocyte autoantibodies of the gammaG class.