The specificity of leukocyte and platelet alloantibodies in sera of patients with nonhemolytic transfusion reactions. Absorptions and elution studies

Current issues with platelet transfusion in patients with cancer

For the past 30 years, platelet transfusions have been used in the treatment of thrombocytopenia caused by decreased production, inadequate function, or increased destruction of platelets. The number of platelet transfusions has increased more than transfusions of other blood components, shifting from whole blood use for the platelet source to plateletpheresis. Hematology/oncology patients are among the largest group receiving platelet transfusions, primarily because the more aggressive chemotherapies produce more acute and prolonged thrombocytopenia. While platelet transfusions often rescue patients with very low platelet levels, they are associated with the risk of viral and bacterial infections, as well as alloimmunization. Platelet donor recruitment can also be difficult, and platelet transfusion can be very expensive depending on the source of platelets. As a result, prophylactic transfusions are less likely to be administered at higher platelet counts, reducing platelet use and cost of platelet transfusions. However, cancer patients receiving intensive chemotherapy or myeloablative regimens require multiple platelet transfusions. For these patients, alternate strategies are needed so that platelet transfusions can be significantly reduced or eliminated.

Elimination of cytokine production in stored platelet concentrate aliquots by photochemical treatment with psoralen plus ultraviolet A light

BACKGROUND

Cytokines generated in platelet concentrates (PCs) during storage have been implicated as possible mediators of febrile nonhemolytic transfusion reactions. Two potential methods of white cell inactivation were compared for their ability to reduce cytokine synthesis in pooled random-donor PC aliquots: treatment with gamma-radiation and photochemical treatment (PCT) using psoralens and ultraviolet A light.

STUDY DESIGN AND METHODS

ABO-matched PC aliquots were pooled and divided into separate aliquots. Aliquots (20 mL) were taken from each pool to serve as an untreated control and to undergo gamma-radiation. Aliquots were treated by using either gamma-radiation (2500 or 5000 cGy) or virucidal PCT. PCT with the psoralens 8-methoxypsoralen (8-MOP), aminomethyltrimethyl psoralen (AMT), and S-59 was investigated. PC aliquots were stored for 7 days and analyzed for levels of interleukin 8 by use of an enzyme-linked immunosorbent assay. Levels of DNA adduct formation were determined by using 3H-labeled psoralens.

RESULTS

Levels of interleukin 8 in the untreated random-donor PC aliquots increased with increasing white cell counts, but they were not affected by pooling. The untreated control aliquots and the aliquots treated with gamma-radiation had significant increases in levels of interleukin 8 after 5 to 7 days of storage (p<0.05). PCT with S-59 resulted in a significant reduction in cytokine synthesis (p<0.05). Day 5 to 7 levels of interleukin 8 did not differ significantly from Day 0 levels. Inhibition of interleukin 8 production by PCT increased with increasing levels of DNA modification (S-59 > AMT > 8-MOP).

CONCLUSION

PCT that utilizes S-59 has been developed to inactivate potential viral and bacterial pathogens in PC aliquots while maintaining in vitro platelet function. These data demonstrate that PCT of aliquots of pooled PC aliquots before storage also prevents white cell cytokine synthesis during storage. PCT may therefore offer the potential for reducing cytokine-associated febrile nonhemolytic transfusion reactions.

Platelet transfusion reaction associated with interdonor HLA incompatibility

An HLA-compatible platelet transfusion was followed by chills, fever, and severe respiratory distress in a multitransfused patient with chronic lymphocytic leukemia. During the previous 7 days the patient had received blood products without incident, including 8 units of red blood cells (RBC), 24 units of pooled random donor platelet concentrates, and five HLA-compatible platelet pheresis products. The patient had no demonstrable RBC, HLA lymphocytotoxic, platelet or granulocyte antibodies. The platelet donor, a multiparous female, had no granulocyte or RBC antibodies but had lymphocytotoxic antibodies against HLA-A2 CREG (cross-reacting group A2, A28, A23, A24) which reacted not with lymphocytes of the patient but with lymphocytes of the donor whose RBC were transfused 24 h prior to the platelet transfusion reaction and whose HLA type is A23, A24; B44, B57. No RBC donors had HLA lymphocytotoxic, granulocyte, or platelet antibodies against the platelet donor. The patient received three subsequent platelet transfusions from the same donor after removal of the antibody-laden plasma with no adverse reaction. These data suggest an interdonor reaction caused by the presence of cells from the RBC donor received by the patient 24 h prior to the transfusion of donor lymphocytotoxic antibody to HLA-A2 CREG antigens.

Leukocyte-poor blood

The conventional techniques used to prepare leukocyte-poor red cell concentrates are described. These techniques conveniently group by their primary processing modalities which are centrifugation, freeze thawing, cell washing, and filtration. Each of these procedures has unique logistical requirements. The complexity, need of dedicated capital equipment, and stringent quality assurance requirements make the use of some of these techniques impractical for the hospital blood bank laboratory. The majority of patients benefit from the receipt of leukocyte-poor blood products prepared by an "in-line" microaggregate filtration technique. Those patients with symptoms which prove to be refractory to microaggregate-filtered blood products and those who require highly purified red cell concentrates to forestall sensitization to transplantation antigens should receive blood prepared either by the cryopreservation/deglycerolization technique or by cotton wool filtration.

A new method of autotransfusing blood drained after cardiac surgery

Ideally, autotransfusion after cardiac surgical procedures should offer the protection of underwater-seal drainage and involve additional cost to the patients only if their blood is reinfused. A technique of returning the patient's postoperatively drained blood that employs these features and that we have found to be safe, simple, and cost-effective is presented.

The serology of febrile transfusion reactions

Sera from 40 patients with febrile, nonhemolytic transfusion reactions were tested for the presence of alloantibodies using a number of techniques, including immuno-fluorescence tests on granulocytes, lymphocytes and platelets, a modified NIH lymphocytotoxicity test and the leukocyte agglutination test. Cells of at least 9 donors were used as target cells. Alloantibodies were detected in all sera. The frequency of the occurrence of antibodies was not much higher in sera obtained about 1 month after the transfusion reaction as in sera obtained within 4 days. Most of these antibodies were anti-HLA, but quite frequently platelet-specific antibodies were found, and sometimes these were the only antibodies detected. Granulocyte-specific antibodies were the least frequent. The nature of the antibodies was specified by their difference in reactivity with the cells of multiple donors, by applying panels of cells from typed donors and by absorption and elution experiments. It appeared that not only granulocyte-specific but also HLA- and perhaps platelet-specific antibodies may be responsible for a febrile transfusion reaction. We did not find that the occurrence of rigors, together with fever, was associated with particular serologic results.

Anti-HLA specificity determined by serum absorption with antigen-masked lymphocytes

Lymphocyte or platelet absorption of multispecific sera is frequently used to establish HLA antibody specificity. Absorption of such sera with cells containing the desired antigenic combinations is often limited by the availability and the HLA characteristics of fresh or frozen cell panels. The method described permits improved absorption of specific HLA antibody with a preparation of cells containing a predetermined single HLA antigen. The procedure involves the screening of the patient's active sera against a panel of frozen cells. Analysis of the positive and negative reactions allows tentative assessment of recipient serum specificities. Cells with a single available HLA antigen type are prepared for serum absorption by suspending the cells in selected antisera to block (mask) HLA surface antigens while leaving just one type of antigen free for monospecific absorption. Following absorption of the test serum with the masked cells, the absorbed serum is then retested against the original panel of frozen cells. Should the results of this screen show a loss of a single HLA activity, the suspected specificity is assigned to the recipient's serum. The use of HLA antigen-masked lymphocytes has proven useful in the definition of HLA antibody specificity.

The role of alloimmunization in platelet survival studies

The role of platelet alloimmunization in the survival of 51Cr-labeled allogeneic platelets was investigated in 89 patients with severe thrombocytopenias. The serological analysis included HLA typing of patients, screening of their sera in the lymphocytotoxicity test (LCTT), the platelet complement fixation test (PCFT), and the platelet radioactive anti-IgG test (PRAT; N = 38). Platelet donors were selected according to the best available HLA match and crossmatch in LCTT. Alloantibodies against HLA antigens were found in the sera of 17 patients (19.1%). No platelet-specific alloantibodies were detected. The use of compatible, allogeneic platelets permitted the discrimination of diminished platelet production from increased platelet turnover in thrombocytopenic patients with proven alloimmunization. Our results stress the necessity of a serological workup prior to platelet survival studies.

Lymphocytotoxic antibodies in patients receiving granulocyte transfusions

The presence of lymphocytotoxic antibodies was studied in 22 patients receiving granulocyte transfusions. Due to previous blood transfusions 7 out of 22 patients had lymphocytotoxic antibodies before granulocyte transfusions were started. 6 out of 15 unsensitized patients developed antibodies during granulocyte transfusion therapy, and 9 out of 15 patients had no detectable antibodies at any time. Transfusion reactions occurred in the presence of lymphocytotoxic antibodies not directed against donor cells.

Complement-dependence of platelet serotonin release test in polytransfused patients

The research of platelet isoantibodies in patients with Cooley's anaemia was performed by simultaneous determination of the platelet-complement fixation test, platelet factor 3 availability assay and 14C-serotonin release test. In 93% of the examined patients we obtained positive results with the 5HT-release test, which appeared to be a complement-dependent reaction in most of the sera-containing isoantibodies, different from sera of patients affected by autoimmune thrombocytopenia.

Specific interaction of HLA antibodies (eluates) with washed platelets

The mechanism of complement-independent action of HLA-A2 antibodies (eluates) on washed platelets was investigated. HLA-specific alteration was confirmed by serological (platelet micro-complement fixation), morphological (platelet spreading) and functional parameters (platelet aggregation, inhibition of collagen-induced platelet aggregation, [14C]serotonin release). In the presence of fibrinogen and calcium ions, HLA antibodies induced instantaneous platelet aggregation and release. Although no morphological (spreading) and functional changes (collagen-induded aggregation) were seen, these platelets did not aggregate or release when fibrinogen was subsequently added. When platelets--in the presence of fibrinogen--were incubated with antibody concentrations too low to induce platelet aggregation or release, specific reduction of platelet reactivity was observed by subsequent collagen aggregation. HLA-specific action of antibodies on washed platelets was inhibited by apyrase and acetyl-salicylic acid, indicating an active participation of platelets in HLA antibody-induced platelet alteration.

Heterogeneity of antibody response to human platelet transfusion

To study the antibody response to human platelet transfusions, nine thrombocytopenia patients with bone marrow failure were given 6 U (3X10(11)) of random platelet concentrates twice a week. Before transfusion, none of the patients had preexisting antibodies detectable with lymphocytotoxicity, platelet aggregation, or capillary leukoagglutination techniques. After receiving 18-78 U of platelets, they became refractory to further transfusions of random platelets and alloantibodies were detectable. Two patterns of antibody response could be identified. In three patients, the sera were not lymphocytotoxic with a panel of standard cells in which all the known HLA antigens in the first and second series were represented at least once. Yet, they caused platelet aggregation with 30, 24, and 60%, respectively, of a donor population studied. The aggregating activities were inhibited by antihuman IgG but not by antihuman IgA or antihuman IgM antiserum. The aggregating antibodies could be absorbed out with donor platelets but not lymphocytes or granulocytes. Antibodies from two of these patients aggregated platelets of their respective siblings matched for both HLA haplotypes. Transfusion of platelets from these two siblings did not increase the platelet count while platelets obtained from aggregation-negative donors did. The sera from the remaining six patients were lymphocytotoxic with 15-100% of the panel of standard cells. They also had aggregating antibodies, which could be absorbed out by both platelets and lymphocytes, suggesting that they were HLA antibodies. These data suggest that the development of platelet-specific antibodies may play an important role in the immunological rejection of isologous platelets, and should be considered in the selection of donors for patients who are refractory to platelets from random donors.

Detection of platelet isoantibodies by (3H)serotonin platelet release and its clinical application to the problem of platelet matching

The detection of platelet isoantibodies by the release of (3H)serotonin from platelets has been evaluated. The conditions for optimal release of (3H)serotonin with platelet isoantibodies using a microtechnique have been defined. A group of cardiac surgery patients were followed pre- and post-transfusions, with 48percent developing a positive serotonin release assay. Of these patients, 16percent also had a platelet complement-fixing and/or lymphocytotoxic isoantibody. There was variation in the degree of correlation between (3H)serotonin release and lymphocytotoxicity using individual National Institutes of Health typing serum. The matching obtained between family members by both techniques showed a close correlation when each technique was evaluated separately using the same NIH typing serum. The detection of iso-antibodies in patients with hematological malignancies correlated with the unresponsiveness to unmatched platelet transfusions in 15 out of 17 cases. The use of the patient's isoantibody to matched platelets of family members by (3H)serotonin release correlated well with the clinical response to transfusion with these platelets. The data suggest that (a) platelet isoantibodies can be detected with increased frequency by (3H)serotonin release; (b) (3H)serotonin release is a specific reaction depending on the surface antigen of the platelet; and (c) the method can be used to match compatible family members for platelet transfusions.