INTERACTIONS BETWEEN 131-I TRACE-LABELLED COLD AGGLUTININ, COMPLEMENT AND RED CELLS

C'1 ESTERASE EFFECT ON ACTIVITY AND PHYSICOCHEMICAL PROPERTIES OF THE FOURTH COMPONENT OF COMPLEMENT

Highly purified C'1 esterase of human serum is capable of inactivating isolated fourth component of human complement (β_1E-globulin). Inactivation is accompanied by changes in electrophoretic and ultracentrifugal properties of β_1E-globulin. If non-sensitized sheep erythrocytes are present during the action of C'1 esterase on β_1E-globulin, a complex is formed consisting of cells and cytolytically active fourth component (EC'4). Thus, inactivation of β_1E-globulin by C'1 esterase appears to be preceded by a state of activation enabling β_1E-molecules to combine with cell membrane receptors. Acceptor groups appear to be present also in 7S γ-globulin and in β_1E-globulin itself, since C'1 esterase can induce the formation of β-β and of β_1E-7S γ-globulin complexes.

Inherited disorders of complement

Isolated complement component deficiencies are uncommon. Deficiencies of all eleven components and two inhibitors of the classical pathway have been described. Complete absence of the components of the alternative pathway has not been described. The consequences of a single defect in complement are often predictable from an understanding of the biologic activities associated with activation of the complement system. Deficiency of C1 esterase inhibitor gives rise to the disease, hereditary angioedema; deficiency of the early components of the classical pathway are associated with lupus erythematosus; C3 and C3 inactivator deficiencies with pyogenic infections; C5 dysfunction with Leiner's disease; deficiencies of the terminal components with recurrent Neisseria bacteremia; and C9 deficiency with normal health. The complement system and its associated biologic activities are reviewed. The present knowledge of the inherited complement deficiencies and associated diseases, with particular emphasis on the dermatologic manifestations, genetics, and diagnosis, is summarized.

I and i antigens on normal and leukemic leukocytes

Human leukocyte I and i antigens were quantitated using 125I labelled purified antibodies. Binding of these antibodies to leukocytes was dependent on reduced temperature. No significant difference in antigen content was observed between normal and leukemic myeloid leukocytes. B lymphocytes bound much greater amounts of both I and i antibodies than did T lymphocytes. Neoplastic lymphoid cells bound widely divergent amounts of both antibodies with chronic lymphocytic leukemia and lymphosarcoma cell leukemia cells binding much decreased amounts compared to normal lymphocytes. Cells from patients with hairy cell leukemia bound very large quantities of these antibodies in a cold dependent fashion. These elevated levels of binding were not due to nonspecific binding of IgM.

Preparation of test cells for the antiglobulin test

Erythrocytes may be coated with blood group antibodies with or without reacting complement or sometimes apparently with complement alone. This may occur in vivo in such conditions as autoimmune acquired haemolytic anaemia, haemolytic disease of the newborn, or after transfusions of incompatible blood. It may occur in vitro also by the deliberate sensitization of erythrocytes during laboratory serological investigations. Blood group antibodies may be of immunoglobulin types gammaM, gammaA, or gammaG; we have never seen gammaD antibodies. The presence of these antibodies on the erythrocyte surface, together with complement components or the presence of complement components alone, may be detected by the direct antiglobulin test where sensitization occurs in vivo or by the indirect antiglobulin test where there is sensitization in vitro.

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: 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.

Serum-red cell interactions at low ionic strength: erythrocyte complement coating and hemolysis of paroxysmal nocturnal hemoglobinuria cells

Complement coating and hemolysis were observed when erythrocytes from patients with paroxysmal nocturnal hemoglobinuria (PNH) were incubated in isotonic sucrose solution in the presence of small amounts of serum. Normal cells were likewise coated with complement components but did not hemolyze. Both normal and PNH erythrocytes reduced the hemolytic complement activity of the serum used in this reaction. Experience with other simple saccharides and related compounds suggests that the low ionic strength of the sucrose solution is the feature that permitted complement coating of red cells and hemolysis of PNH erythrocytes. Isotonic solutions of other sugars or sugar alcohols that do not readily enter human erythrocytes could be substituted for sucrose. The mechanism for these reactions may possibly relate to the agglutination observed with erythrocytes tested in the serum-sucrose system. Even though PNH hemolytic activity could be removed by prior heating of serum or barium sulfate treatment of plasma, the agglutination phenomenon still persisted. The in vitro conditions necessary for optimal sucrose hemolysis of PNH erythrocytes were described and compared with those of the classical acid hemolysis test. The requirement for less serum in the sucrose hemolysis system than needed in the standard acid hemolysis reaction makes certain experiments, especially those using large amounts of autologous PNH serum, much more feasible. Additional advantages of the sucrose hemolysis test are that it can be carried out at room temperature in the presence of oxalate and citrate and that critical pH control is not essential. To date, the sucrose hemolysis test has been a sensitive and specific one for PNH. A modified test used for screening purposes, the "sugar water" test, is very easy to perform.

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'.