STUDIES WITH RADIOIODINATED COLD AGGLUTININS OF TEN PATIENTS

Cold target competition analysis of the classical activation pathway of complement-mediated cytotoxicity: a non-interaction model for competing lysis

A mathematical analysis of cold target competition experiments of complement-mediated lysis is presented, aimed at developing a minimal model of lysis where no interaction between the competing populations of sensitized blood group A and B erythrocytes is presumed. The model is able to predict the extent of lysis from the input values with remarkable accuracy suggesting that under the conditions used no stimulation and/or inhibition of the lysis of the sensitized erythrocytes occurs. The distribution of complement between the competing A and B erythrocyte populations is approximated by the model and found to be proportional to the 5th and 4th power of the ratios of the antibody and target cell concentrations, respectively. In accordance with earlier observations, suggesting that the interaction between the antibody and the C1q molecules is based on polar electrostatic charges, we propose that the sensitizing antibody provides an electrostatic field around the erythrocytes which attracts C1q molecules towards their membranes.

Complement activation by cold agglutinins

Purified monoclonal human IgM cold agglutinins (CA) of different specificities (anti-I, anti-i, anti-Pr) were investigated for their complement-activating capacity in a homologous system. Incubation of human RBC with excess of IgM CA in the cold, and subsequently with human serum at 37 degrees C, resulted in striking differences in hemolysis. Hemolysis did not correlate to the amount of antibodies bound to RBC at 4 or 20 degrees C. Despite the hemolytic inefficiency of anti-i and anti-Pr CA tested, C1 fixation and subsequent activation of the classical pathway of complement could be assessed in all cases. Absolute numbers of C3 molecules bound to RBC, exceeding the critical level to initiate the terminal sequence of the complement cascade, could not fully explain the differences in the hemolytic activity of the CA. Since C8 binding protein (C8bp) carries I determinants it is hypothesized that anti-I-induced complement-mediated hemolysis might also be favored by the binding of the autoantibody to and probably steric hindrance of this major regulatory protein of the terminal complement sequence. The prominent role of homologous restriction of complement-mediated lysis as a protective mechanism can also be deduced from the fact that rabbit as well as rat serum as a source of heterologous complement lysed cold agglutinin-sensitized red blood cells more efficiently than human serum.

The significance of complement in immunohematology

In vitro detection of red cell-bound complement can be important in the differential diagnosis of autoimmune and drug-induced immune hemolytic anemias; it can also be a sensitive test for the detection of complement-binding alloantibodies, e.g., in compatibility testing. Red cell-bound complement can be detected by the antiglobulin test if suitable antiglobulin sera (AGS) are utilized. In 1971, the Federal Standards for AGS were criticized because so-called broad spectrum AGS used routinely in blood banks were shown to often be deficient in anticomplement reactivity. In the new few years commercial regents changed with regard to the quantity and specificity of their anticomplement components. A great deal of controversy developed as to the true importance of detecting red cell-bound complement, the particular fragments of complement that should be detected, and the causes of nonspecific reactions that seemed to be occurring, especially with the increasing usage of new techniques utilizing low ionic strength media. When monospecific anti-IgG and anti-C3 became available commercially, the controversy regarding diagnostic testing was resolved as direct antiglobulin testing could be performed with these reagents rather than the broad spectrum reagents. Two main questions remained: how rare are alloantibodies that are only detectable by the anticomplement component of AGS? How clinically significant are such antibodies? The results of our 3-year study indicated that such antibodies (usually anti-Kidd) occurred with a incidence of 1/8000 sera tested. Some of these antibodies seemed capable of shortening the life span of transfused red cells, as determined by 51Cr survival studies; some showed negligible cell destruction. Severe transfusion reactions due to such antibodies would seem unlikely. Individual laboratories will have to balance the risk of missing some complement-dependent antibodies of possible clinical significance with the increased nonspecificity encountered in their own laboratory with AGS containing anticomplement.

Immunoblastic lymphoma: an immunologic study

An immunologic study of a 59-year-old man with immunoblastic lymphoma is presented. Shortly after his hospital admission, an uncompensated hemolytic process developed, caused by cold agglutinins. These antibodies had anti-i specificity, were of low titer at cold temperature, but demonstrated a high thermal amplitude. An apparent paraprotein was found by further immunochemical analysis to be polyclonal. The majority of cells in the peripheral blood (over 2000/cu nm), lymph node, and bone marrow that contained cytoplasmic IgG or IgM were plasma cells, although a small number of cells resembled lymphoblasts. Their staining with anti-lambda and anti-kappa chain reagents confirmed the polyclonality of the immunoglobins. Some plasma cells displayed the concomitant presence of both IgM and IgG immunoglobulins. Free immunoglobin was also demonstrated intercellularly in the lymph node section. The patient's acute hemolysis was controlled by plasmapheresis and eventually by combination chemotherapy. After chemotherapy, the clinical improvement was rapid, immunoglobulin levels returned to normal, and the patient remains asymptomatic 40 months after completing six courses of combination chemotherapy. This report provides evidence for polyclonal proliferation of B-lymphocytes in immunoblastic lymphoma.

Cold agglutinin disease

Development of the Coombs test has led to rapid progress in the recognition of various autoimmune hemolytic anemias. Cold agglutinin disease, a relatively rare disorder, occurs in idiopathic and secondary forms, the latter often in association with diseases that alter the immune status. The higher the titer of cold agglutinin, the greater is the thermal range of its activity. One of the characteristic clinical manifestations of the disease is striking cyanosis in acral areas on exposure to cold, which abates quickly on warming. This parallels the accelerated hemolysis at cold temperatures, which is reversible as heat is applied. In some patients, however, the disease is covert and is discovered only incidentally. The report of such a case is included.

Antibody detection and identification in a hospital blood bank

A six-year serological survey has demonstrated that an average of 2.2% per annum of individuals requiring compatibility testing possessed antibodies de novo and that the frequency for individuals forming antibodies following transfusion is 4.1%. The increased detection rate from 1.5% (1969) to 4.1% (1971-5) was almost entirely due to the sensitivity of the two-stage papain technique; a total of 124 antibodies were detected only in this test. Three of these enzyme-active antibodies were found to be the cause of mild haemolytic transfusion reactions. Since 60% of the listed 332 alloantibodies were Rh-specific, the transfusion of appropriately Rh phenotyped blood is strongly recommended.

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.

Chronic hemolytic anemia due to cold agglutinins. II. The role of C' in red cell destruction

The sera of four patients with chronic hemolytic anemia due to cold agglutinins deposited C' globulins on normal red cells at 37 degrees C. The circulating cells of the patients were heavily coated with C' complex and were relatively resistant to C' hemolysis by cold agglutinin. Such red cells were removed from the patients' circulation at an exponential rate with (51)Cr t((1/2)) that varied from 7 to 19 days. Normal red cells were removed rapidly by hepatic sequestration during the first hours in the patients' circulation. Thereafter, a slower rate of abnormal destruction occurred which was associated with the accumulation of C' complexes on the red cell and the development of resistance to C' hemolysis by cold agglutinin. Normal red cells coated with sufficient C' complex by action of cold agglutinins in vitro to produce resistance to C' hemolysis by cold agglutinins demonstrated varying degrees of improved survival during the first hours in the circulation of three of the patients. The levels of serum C' were reduced in all four patients with chronic hemolytic anemia due to cold agglutinins. Transfusion of large volumes of normal red cells into two patients further reduced serum C'. (51)Cr-labeled normal red cells survived longer after red cell transfusions than before, because of less rapid destruction during the first hours in the circulation. The reduction in serum C' levels appeared responsible for the improved survival. In subjects without cold agglutinins, the presence of the spleen decreased the survival of red cells from a patient who had previously undergone splenectomy. Splenic removal also predominated in the reduced survival of autologous red cells in one patient. Neither hepatic nor splenic mechanisms predominated in removing autologous C'-coated cells in the other two patients.

Chronic hemolytic anemia due to cold agglutinins: the mechanism of resistance of red cells to C' hemolysis by cold agglutinins

The red cells of patients with chronic hemolytic anemia due to cold agglutinins are agglutinated by antiglobulin serum in a nongamma reaction due to the coating of beta-globulins, C'4 and C'3. The red cells of such patients are abnormally resistant to C' hemolysis by cold agglutinin. Normal red cells can be made equally resistant to C' hemolysis by incubation with cold agglutinin and normal serum at temperatures which allow transient reactions between the red cells and cold agglutinins. The development of resistance to C' hemolysis was related to increasing susceptibility to agglutination in anti-beta(1c)- and anti-beta(1e)-sera and by increasing uptake of (131)I activity from labeled anti-beta-globulin serum containing antibodies for both globulins. There was decrease in the adsorption of (131)I-labeled cold agglutinin during the development of resistance to C' hemolysis and reduced susceptibility to agglutination by cold agglutinins. Since cold agglutinins have been demonstrated to dissociate from the red cell, leaving fractions of C' globulin attached, it is postulated that repeated transient reactions produce the accumulation of incomplete C' complexes. Steric hindrance by the adsorbed C' complexes is probably responsible for the inhibition of the reaction with cold agglutinin. There is evidence that the adsorbed C' complexes also interfere with the hemolytic action of C' even when cold agglutinin has become reattached to the red cells. The accumulation of C' complexes by cold agglutinins appears to be the most important factor in the abnormal resistance to C' hemolysis exhibited by the patient's red cells. Other factors, such as the heterogeneity within a population of normal cells, appear to be of minor significance.

Immune lysis of normal human and paroxysmal nocturnal hemoglobinuria (PNH) red blood cells. 3. The membrane defects caused by complement lysis

1. The defects produced on the membrane of the human red blood cell by the action of complement and antibody have been studied by the use of the electron microscope. These are round to slightly ovoid holes and are surrounded by an irregular ring, about 20 A thick. The mean diameter of the holes is about 103 A if human complement is used (regardless of the antibody used for sensitization) and about 88 A if guinea pig complement is used. 2. The holes in normal and PNH red cells appear to be identical, under the same conditions. The membrane defects produced by lysis of PNH cells with acidified normal serum (the Ham's test) are identical to those produced by complement lysis with specific antibody, indicating that complement is undoubtedly the cause of such lysis. 3. Evidence is presented that when human complement acts on human red cells sensitized with anti-I antibody, each complete activation of complement leads to the production of a cluster of holes. This contrasts to the action of guinea pig complement, on sheep cells, each activation of which leads to a single hole. 4. The maximum number of anti-I antibody molecules which can attach to a human red cell (i.e. the minimum number of antigen sites) is about 500,000 for both normal and PNH cells. 5. The number of holes produced during lysis of the PNH cell is the same as that of the normal cell. When all cells are lysed by am excess of C', a mean of about 90,000 holes are present on each membrane. When complement is limited, a larger proportion of PNH cells are lysed due to their peculiar sensitivity to C' but the number of holes on each lysed cell is the same as for normal cells lysed by the same concentration of C'.