Studies on the preservation of red blood cells. Attachment of the third component of human complement to erythrocytes during storage at 4 degrees C

Antibodies to Senescent Antigen and C3 Are Not Required for Normal Red Blood Cell Lifespan in a Murine Model

Red blood cells (RBCs) have a well-defined lifespan, indicating a mechanism by which senescent cells of a certain age are removed from circulation. However, the specifics by which senescent cells are recognized and removed are poorly understood. There are multiple competing hypotheses for this process, perhaps the most commonly cited is that senescent RBCs expose neoantigens [or senescent antigen(s)] that are then recognized by naturally occurring antibodies, which opsonize the senescent cells and result in clearance from circulation. While there are a large volume of published data to indicate that older RBCs accumulate increased levels of antibody on their surface, to the best of our knowledge, the causal role of such antibodies in clearance has not been rigorously assessed. In the current report, we demonstrate that RBC lifespan and clearance patterns are not altered in mice deficient in antibodies, in C3 protein, or missing both. These data demonstrate that neither antibody nor C3 is required for clearance of senescent RBCs, and questions if they are even involved, in a murine model of RBC lifespan.

Relationship between the third component of human complement (C3) bound to stored preserved erythrocytes and their viability in vivo

In this study we evaluated whether the 4 degrees C storage-induced coating of red blood cells (RBC) with molecules of the third component of human complement, C3, affects the viability of the preserved RBC. To this end, we determined whether the amount of C3 bound to preserved RBC correlated with the 24-hour survival value. The % anti-C3c-induced agglutination of stored RBC provided an estimate of the amount of RBC-bound C3. In some cases, the number of RBC-bound C3c-containing molecules was also quantitated. The 24-hour survival of autologous RBC was measured in 114 cases. All units were initially stored at 4 degrees C as RBC concentrates followed in 21 cases by frozen storage and in 75 cases by biochemical rejuvenation and frozen storage. The data showed a significant correlation between % anti-C3c-induced agglutination of the preserved RBC and the length of 4 degrees C storage of the RBC concentrates. Neither freezing nor rejuvenation cleaved the C3c fragment from stored RBC. The 24-hour survival was significantly and negatively correlated with both the storage length of RBC concentrates at 4 degrees C and with the amount of RBC-bound C3 but not with RBC ATP level. These data suggest that the RBC-bound C3 either contributes to or is a marker for the extent of the preservation injury of RBC.

Measurement of fragments of the third component of human complement on erythrocytes by a new immunochemical method

This paper describes a new antiglobulin consumption method to quantitate the fragments of the third component of human complement (C3) on red blood cell (RBC) membranes. Zymosan-bound C3, which can be stored frozen at -80 degrees C for years, was used as a standard in these tests. Using anti-C3c antibody, zymosan-bound C3 could be calibrated against soluble converted C3 (beta 1A), but not against soluble, native C3 (beta 1C). Calibration with several commercial serum standards yielded virtually identical values. Approximately 79.8 +/- 28.2 C3d molecules (mean +/- 1 SD, n = 50) were detected on normal, freshly collected RBC by this method, whereas no C3c fragments were noted. EC43, prepared by dilution of blood samples with low ionic strength solution, had between 650 and 3,100 C3 molecules/RBC when measured with anti-C3c and between 1,140 and 6,500 C3 molecules when measured with anti-C3d. These data indicated that part of the C3b molecules on EC43 had cleaved to C3d. EC43 are reported to have up to 200,000 C3 molecules when measured by other techniques. To resolve this discrepancy, EC43 were prepared by dialysis of blood samples against low ionic strength solution. About 97.5% of C3 remained in plasma after dialysis supporting the results of our tests. The new assay is an accurate and sensitive method of quantitating C3 fragments bound to RBC in vivo and in vitro.

Complement in CPD-stored blood

We studied complement functions, breakdown of C3 and aggregation of immunoglobulins in whole blood stored in citrate phosphate dextrose at 4 degrees C for up to 3 weeks from 10 normal blood donors. No significant changes in total haemolytic complement (CH50) and alternative pathway haemolytic complement activity were detected. However, the complement-mediated capacity of the sera to solubilise a pre-formed immune precipitate decreased significantly at 2 and 3 weeks (p less than 0.02 at 2 weeks, p less than 0.003 at 3 weeks). No C3 conversion could be detected by immunoelectrophoresis but alteration in C3 was attested by a significant increase in breakdown products of C3 by 1 week (p less than 0.002) and all were above the normal range after 3 weeks (p less than 0.0001). No aggregation of immunoglobulins could be detected using two immune complex assays.

Complement and Ig uptake by erythrocytes in low ionic strength solutions

We studied the uptake of immunoglobulin (Ig) and complement from plasma by red blood cells (RBC) under low ionic strength (LIS) conditions using Rh-negative RBC and anti-Rh antibodies. The ionic strength of plasma/RBC mixtures was lowered by dialysis against 5% mannitol, pH 6.0. The studies revealed that bromelin-modified RBC failed to bind either Ig or complement in low ionic strength conditions, but that unmodified RBC bound the majority of anti-D. The bound anti-D (consisting of IgG1, IgG3, IgA, and IgM molecules) could be eluted into 0.9% NaCl yielding a higher recovery of antibody than that obtained by specific absorption-elution techniques. Although uptake of Ig by RBC was independent of complement activation, the subsequent elution of bound Ig into normal ionic strength solutions was not. Small amounts of Ig remained on EC43 and EC4, but not on RBC that did not become complement sensitized during low ionic strength exposure. These findings suggest that Ig remained attached to RBC via a complement-RBC bond.