Mechanisms of Immune Lysis of the Red Cells in Hereditary Erythroblastic Multinuclearity with a Positive Acidified Serum Test and Paroxysmal Nocturnal Hemoglobinuria

Abstract

A B S T R A C T The red cells of patients with hereditary erythroblastic multinuclearity with a positive acidified serum test (HEMPAS), a form of congenital dyserythropoietic anemia, and the cells of patients with paroxysmal nocturnal hemoglobinuria (PNH) are lysed more readily than normal cells by certain antibodies, notably cold agglutinins (anti-I) and complement. With some but not other examples of anti-I, HEMPAS and PNH cells adsorbed more antibody than normal cells. Equal quantities of adsorbed antibody bound equal quantities of the first component of complement (Cl) to normal, PNH, and HEMPAS cells. However, for a given quantity of bound antibody and C1, much more of the fourth component of complement (C4) was bound to HEMPAS cells than to normal cells. This resulted in the binding of proportionately larger quantities of the third component of complement (C3) to these cells. The same amount of bound C3 was found on the membranes of normal and HEMPAS cells for a given degree of lysis. Hence, the marked increase in lysis of HEMPAS cells is due to the increased adsorption of antibody and/or increased binding of C4.PNH cells bound the same amount of C4 per bound C1 as normal cells but bound more C3 than normal cells. However, the mean concentration of C3 on the membrane of PNH cells was one-third to one-fifth that on normal cells for a given degree of lysis. Hence, the increased lysis of PNH cells is due to the increased binding of C3 and increased hemolytic effectiveness of the bound C3.

Quantitative influence of antibody and complement coating of red cells on monocyte-mediated cell lysis.

“…Complement-coated cells were assayed for total C3 using a method previously described (14). The assay measures inhibition of lysis of C3-coated, trypsinized sheep cells by anti-C3 in the presence of guinea pig serum in a manner analogous to the IgG assay.…”

“…In sensitizing a series ofrabbits with C3 antigen by methods previously described (14), the antiserum from a single rabbit was found to detect antigens present on native C3, and on C3b-and C3d-coated red cells. The The time-course of lysis ofanti-D-coated, washed red cells was rapid, with 70-80% of total observed lysis completed within 3.5 h (see Fig.…”

“…We have developed quantitative IgG and C3 antiglobulin consumption tests capable of measuring very small amounts of IgG (13) and C3 (14), and we have utilized these assays to determine the quantitative requirements of IgG and C3 coating to produce lysis of human red cells incubated with human peripheral blood mononuclear cells in vitro. The relative effi-ciency of anti-D and naturally occurring anti-A or anti-B and the effect of complement coating on lysis in the presence and absence ofunbound fluid phase IgG were examined and are reported in detail.…”

Paroxysmal Nocturnal Hemoglobinuria and Glycosyl Phosphatidylinositol Anchored Proteins That Regulate Complement

“…The first definitive evidence of the nature of the aberrant interactions of complement with PNH erythrocytes was provided by a series of elegant experiments reported by Rosse and colleagues (3,4). Those studies showed that when complement was activated by either the classical or alternative pathway, PNH erythrocytes bound much greater amounts of activated C3 than normal cells.…”

Characterization of the complement sensitivity of paroxysmal nocturnal hemoglobinuria erythrocytes.

“…Both PNH II and PNH III cells fix more complement (C)3b when complement is activated by either the classical or the alternative pathway (3)(4)(5)(6). This greater binding of C3b is due to the enhanced functional activity of the C3 convertase when affixed to these abnormal cells.…”