Archives of Medical Research 33 (2002) 536–540

0188-4409/02 $–see front matter. Copyright © 2002 IMSS. Published by Elsevier Science Inc.PII S0188-4409(02)00412-5

ORIGINAL ARTICLE

Fc Receptor Blockade in Patients with Refractory Chronic Immune Thrombocytopenic Purpura with Anti-D IgG

Raúl Ambriz-Fernández,

a,b

Carlos Martínez-Murillo,

a

Sandra Quintana-González,

a,b

Juan Collazo-Jaloma

a

and Javier Bautista-Juárez

a

a

Banco Central de Sangre, Centro Médico Nacional Siglo XXI (CMNSXXI), Instituto Mexicano del Seguro Social (IMSS), Mexico City, Mexico

b

Centro de Hemostasia y Trombosis, Servicio de Hematología (Unidades 103 y 204), Hospital General de México, Mexico City, Mexico

Received for publication September 13, 2001; accepted June 26, 2002 (01/153).

Background.

This is an evaluation of the treatment of 63 patients with chronic immunethrombocytopenic purpura (54 splenectomized and nine nonsplenectomized) with weeklydoses of anti-D (IgG)-coated red blood cells (RBCs).

Methods.

All patients were given one 5–15

�

g/kg/dose of intravenous (i.v.) anti-D (IgG)-coated RBCs per week (average of 300

�

g/dose/week) for a median 3-month period (3–6months). Treatment modality was evaluated on a weekly basis by platelet counts, measur-ing of hemoglobin levels, and performance of Coombs tests.

Results.

All patients presented a clinical response. Fifty-two patients (82.5%) increasedtheir platelet count (PC) and 45 (69.8%) increased their PC

�

50

�

10

9

/L. In 34 cases, re-sponse was sustained. Six of nine nonsplenectomized patients (67%) increased PC, thusavoiding splenectomy; four patients attained a stable complete response (CR). Similar plate-let responses were observed in homozygous and heterozygous Rh (D)-positive patients(Rh/Hr phenotypes). Currently, after

�

10 years, 43 patients present a now permanentcomplete response with platelet count

�

50

�

10

9

/L. Ten patients subsequently decreasedtheir platelet count, although they were able to attain CR after receiving six doses of anti-D (IgG)-coated RBCs.

Conclusions.

Based on our study of Fc receptor blockade treatment with anti-D (IgG)-coated RBCs with the most difficult cases of ITP, which resulted in a 69.8% successful re-sponse rate, we concluded that weekly prescription of anti-D (IgG)-coated RBCs is an ef-fective approach to treating chronic refractory ITP. © 2002 IMSS. Published by ElsevierScience Inc.

Key Words:

Immune thrombocytopenic purpura, Chronic refractory ITP, FcR blockade, Anti-D(IgG)-coated red blood cells, Immune thrombocytopenic purpura treatment.

Introduction

Chronic immune (idiopathic) thrombocytopenic purpura(ITP) is an autoimmune disorder characterized by phagocy-tosis of antibody-coated (opsonized) platelets by the mono-nuclear-macrophage system (1). In the early 1950s, Har-rington et al. (2) demonstrated that transfusion of blood

from patients with chronic ITP into normal subjects resultedin thrombocytopenia. Subsequent studies by Shulman et al.(3) showed that thrombocytopenic effect was dose-depen-dent and less marked in splenectomized patients and in pa-tients pretreated with corticosteroids or with blockade ofreticuloendothelial system. These

in vivo

studies suggestedthat the antiplatelet antibody was an IgG antibody and thatITP was an autoimmune disease.

The adult form of ITP is often protracted over manyyears and occurs almost exclusively in females. There aremany different methods for treating this agonizing, oftenlifelong, disease. Conventional treatment with corticoste-

Address reprint requests to: Dr. Carlos Martínez-Murillo, Banco Cen-tral de Sangre, CMNSXXI, IMSS, Av. Cuauhtémoc #330, Colonia Doc-tores, 06720 México, D.F., México. Tel.: (

�

52) (55) 5627-2900, ext. 2609;FAX: (

�

52) (55) 5519-2063; E-mail: carlmarz@prodigy.net.mx

Treatment of ITP With Anti-D IgG

537

roids and/or splenectomy generates complete response ratesof 60–70% (4,5).

Patients not responding to either corticosteroids or sple-nectomy constitute a major clinical problem. There is alarge number of therapeutic options available for these pa-tients (6,7), including cyclophosphamide, azathioprine, vin-cristine sulfate, an infusion of vinblastine, danazol, colchi-cine, cyclosporine, dapsone, vitamin C, late prednisone,high-dose intravenous (i.v.) dexamethasone, combinationchemotherapy, surgical removal of accessory spleens,splenic irradiation, plasma exchange, interferon-alpha, im-munoadsorption with protein A, high-dose (i.v.) gammaglobulin (IgG), and i.v. anti-Rh (D) antibodies, etc. (6,7)Repeated clinical studies using a variety of different agentshave shown that Fc receptor (FcR) blockade is an importantmechanism of treatment effect (8).

Salama et al. (9,10) injected Rh (D

�

) ITP patients withanti-D and demonstrated that platelet count (PC) increasedin the majority of Rh (D

�

) patients. These and other au-thors treated several D-positive ITP patients with i.v. anti-Dinfusions and reported remarkably good results (11–15).

Salama et al. (9,10) conducted a study in which Rh (D

�

)ITP patients were injected with anti-D. As a result, most pa-tients increased their PC. Other authors have also reportedimpressive results in D-positive patients treated with i.v.anti-D infusions (11–15).

Anti-D has been used in prophylaxis of Rh isoimmuniza-tion for

�

20 years. However, clinical experience with anti-D in treating ITP is relatively recent. The role of anti-D inFcR blockade in patients with ITP has been confirmed byseveral reports (16–18).

Since 1984, our group has reported experience in use ofautologous anti-D (IgG)-coated RBCs for diagnosing andtreating splenectomized refractory ITP (17–22). In a studyconducted with 16 patients, a single low dose (21) produceda 56% response rate and permanent complete remission in16% of cases (21). This report is an evaluation of our expe-rience in treating FcR blockade in patients with chronic re-fractory ITP with anti-D (IgG)-coated RBCs.

Materials and Methods

Patients.

All patients with chronic refractory ITP studiedand treated at the Banco Central de Sangre of the IMSSCentro Médico Nacional Siglo XXI in Mexico City since1984 were prospectively included in the study. Sixty-threepatients (51 females and 12 males) were treated with anti-D(IgG)-coated RBCs. Fifty-four patients had splenectomizedrefractory ITP; their ages ranged from 4 to 80 years. Criteriafor diagnosis of ITP were previously described (5). No pa-tient had criteria for systemic lupus erythematosus (SLE)and tests for HIV were negative in all cases. Platelet-associ-ated IgG assay was performed in 58 patients and was posi-tive in 40. All subjects had chronic ITP (1–30 years) andtheir cases were refractory to corticosteroid treatments

(platelet responses were

�

50

�

10

9

/L) and to splenectomy,if performed. Several cases had been treated with danazol (

n

�

40), azathioprine (

n

�

19), cyclophosphamide (

n

�

3), i.v.vinca alkaloids (

n

�

4), vinblastine- or vincristine-loadedplatelets (

n

�

3), plasmapheresis (

n

�

1), surgical removalof post-splenectomy accessory spleens (

n

�

5), colchicine(

n

�

5), cyclosporine (

n

�

2), interferon (

n

�

3), and ascor-bate (

n

�

2).

Methods.

A venous blood sample was obtained in steriletubes containing citrate dextrose (9:1, volume:volume). Onemilliliter of sample was used for analysis of Rh antigen. Tenmilliliters of saline solution with 300

�

g of anti-D IgG(Cutter Biological Products Business Unit, Bayer Pharma-ceuticals Business Group, Research Triangle Park, NC,USA) were transferred into a transfer bag. A total of 15 mLof packed red blood cells was exposed to anti-D (100

�

g ofanti-D in 5 mL of packed red blood cells). The mixture wasincubated at 37

�

C for 1 h. Next, the sample was washedtwice with saline solution to eliminate immunoglobulincomplexes and aggregates and with the antiseptic solution(thimerosal) to avoid cumulative and side effects of anti-Dpreparation. A total of 15 mL of this compound was indi-cated and given in a single i.v. dose to patients.

Patients received one 5–15

�

g/kg/dose of i.v. anti-D(IgG)-coated RBCs per week (an average of 300

�

g/dose/week), for a median 3-month period (3–6 months). Thetreatment modality was evaluated on a weekly basis byplatelet count, hemoglobin level measurement, and perfor-mance of Coombs tests. Final response was evaluated afterthe 3-month period with blood cell counts (BCC), hemolytictests, and liver function tests.

Definition of responses.

Criteria for response have beenpreviously described. A responder was a patient withoutbleeding symptoms and with at least a twofold increase inplatelet count. Response to anti-D (IgG)-coated RBCs treat-ment was classified as follows: poor (PC between 25 and 50

�

10

9

/L); partial (PC between 50 and 100

�

10

9

/L); complete(PC

�

100

�

10

9

/L), and no response if no increment in PCwas observed despite several treatments. Regarding re-sponse duration, stable was

�

6 months, and nonstable

�

6months. We conducted a before–after study.

Statistical analysis.

We used Wilcoxon and Mann–Whit-ney

U

tests for statistical analysis.

Results

A total of 63 patients were prospectively included in thestudy, and all patients had a clinical response after 2 weeks(1–2). All initial responses were attained with weekly admin-istration for a period of 3–12 weeks (mean, 6). Spontaneousrecovery was excluded due to observation of a progressiveincrease of platelets with each new anti-D (IgG)-coated

538

Ambriz-Fernández et al./ Archives of Medical Research 33 (2002) 536–540

RBCs treatment. Differences in response of PC mean priorto and after anti-D (IgG)-coated RBCs treatment were sig-nificant (

p

�

0.0001) 95% confidence interval (CI 95%)17.06–25.3.

Fifty-two patients (82.5%) increased their platelet count;44 (69.8%) increased their PC

�

50

�

10

9

/L. In 34 cases, re-sponse was stable (Table 1).

Of nine nonsplenectomized patients, six (67%) increasedtheir PC, thus avoiding splenectomy, and four subjects at-tained a stable CR. Nine patients with nonstable responserequired maintenance with anti-D (IgG)-coated RBCs every2 weeks. Late responses were observed in five patients; how-ever, four patients responded later (after 20 weeks of treat-ment), two with CR and two with partial response (PR). Of54 patients, 48 (89%) increased their PC, 15 attained perma-nent CR, and 23 attained PR. There were no significant dif-ferences between PC of splenectomized and nonsplenecto-mized patients (mean PC 88.3

56.8 vs. 89.6

63.4).Rh/Hr phenotypes of RBCs in 56 patients (six not tested

and one Rh D

) were as follows: 45 were R2/R2, R1/R1, orR1/R2, and 11 were R1/r or R2/r. Patients with R1/R2, R1/R1,and R2/R2 phenotypes obtained 38/45 responses (84.5%)after 3–6 months of treatment, while only 3/11 (28%) of pa-tients with R1/r or R2/r phenotype responded in the sameperiod. When we compared mean PC in Rh/Hr phenotypeheterozygote patients (R2/r, R1/r) and Rh/Hr phenotype ho-mozygote patients (R2/R2, R1/R1, R1/R2), we found nosignificant differences (76.6

67.6 vs. 91

55.7). One Rh(D

) patient was treated with 75 mL of homologous RBCs-D (

�

) R1/r phenotype coated with 1,500

�

g of anti-D perweek for 2 weeks and attained a stable response.

Currently, after

�

10 years, 43 patients attained perma-nent complete response, with platelets

�

50

�

10

9

/L. Tenpatients had a subsequent relapse; nonetheless, they attainedCR after six doses of anti-D (IgG)-coated RBCs.

There were no complications attributable to therapy withanti-D (IgG)-coated RBCs. Fifty patients decreased theirhemoglobin level, but not by

�

0.5 g/dL. There were no in-stances of hemoglobinuria or raised creatinine levels and noother adverse effects of treatment. Studies using Coombstest (CT) in a venous blood sample of patients prior to everyanti-D (IgG)-coated RBCs treatment showed CT positive(1:128–1:256), which demonstrated

in vitro

effectiveness ofRBCs opsonization.

Discussion and Conclusions

Salama et al. (9,10) concluded that the effect of i.v. IgG onPC is due to competition between sensitized red cells andplatelets sensitized with autoantibodies for FcR on splenicmacrophages. This observation was the treatment basis ofpatients with patients with ITP with anti-D IgG. The authorsemployed 30–50

�

g/kg of anti-D and reported success innonsplenectomized subjects with ITP.

Number of remissions among splenectomized patientswith ITP increased when high concentrations of anti-D (IgG)were used with intermittent boostering because Fc-mediated

Table 1.

Results of 63 patients with ITP with anti-D (IgG)-coated red blood cells

No. Sex/ageITP evolution

(years) Splenectomy

PC

�

20

9

/L

Baseline 12 weeks Last count

1 20/F 3 Yes 4 56 1502 59/F 3 Yes 12 10 153 37/M 10 Yes 10 100 2004 75/F 7 Yes 17 20 205 25/F 18 Yes 10 86 906 24/F 6 Yes 17 30 357 35/F 8 Yes 3 10 108 9/F 7 Yes 4 80 989 25/F 4 Yes 10 36 80

10 18/F 13 Yes 10 66 7811 14/F 9 Yes 18 10 1512 31/F 4 Yes 5 51 3213 8/F 3 Yes 18 37 3114 50/F 5 Yes 40 72 9015 30/F 3 Yes 40 66 8016 37/F 7 Yes 24 190 20017 45/M 9 Yes 40 76 10018 54/F 8 Yes 20 98 9819 35/F 20 Yes 40 90 9020 37/F 9 Yes 25 36 6021 14/F 4 Yes 10 23 2222 46/F 13 Yes 34 80 8023 60/M 8 Yes 30 90 9024 19/F 12 Yes 20 118 20025 30/F 8 Yes 35 150 20026 71/F 10 Yes 10 10 1527 71/F 6 Yes 10 35 3528 35/F 8 Yes 10 26 9029 56/F 43 Yes 20 20 3030 16/F 11 Yes 10 10 1031 31/F 7 Yes 5 52 5632 53/F 10 Yes 32 60 6433 20/F 6 Yes

a

35 150 15034 58/F 8 Yes 80 200 20035 17/F 10 Yes 35 150 15036 59/F 2 Yes 12 150 15037 24/M 1 Yes 21 150 15038 16/F 12 Yes 15 30 3039 18/F 7 Yes 25 150 18040 57/M 5 Yes 25 120 15041 28/F 7 Yes 20 130 15042 62/F 15 Yes 32 30 2543 33/F 15 Yes 17 60 8044 46/F 10 Yes 20 70 9045 45/F 3 Yes 5 30 3046 47/F 1 Yes 17 90 9047 18/M 1 Yes 48 20 3048 63/F 4 Yes 30 80 8049 25/M 1 Yes 15 80 8050 48/M 10 Yes 60 80 8051 56/F 8 Yes 7 150 15052 19/F 2 Yes 5 48 6553 26/M 4 Yes

a

69 70 14554 28/F 7 Yes 15 60 8055 4/F 12 No 1 15 1556 9/M 2 No 15 150 15057 80/M 1 No 30 150 15058 16/M 9 No 12 65 6559 43/F 2 No 2 100 15660 4/F 1 No 5 5 561 19/F 6 months No 5 38 3062 71/F 6 months No 7 150 15063 34/F 3 No 53 56 86

a

Accessory spleen.

Treatment of ITP With Anti-D IgG

539

phagocytosis in liver requires a higher degree of cell sensiti-zation than in spleen (1). Earlier reports using autologousRBCs coated

in vitro

with anti-D (IgG) supported excellenterythrocyte sensitization, consistent with the effects of thistherapy in the mononuclear macrophage system of splenec-tomized patients:

99m

Tc-labeled RBCs coated with anti-D(IgG) provided accurate localization of postsplenectomy ac-cessory spleens (18,22,23). High positive titer of direct anti-globulin test (DAT) obtained in anti-D (IgG)-coated RBCs(23) contrasts with other reports of DAT after i.v. and/or in-tramuscular (i.m.) administration of anti-D (11,12,14).

Several mechanisms were proposed for i.v. IgG in lower-ing platelet destruction. Some mechanisms included the fol-lowing: direct altering of platelet receptor mechanism in thereticuloendothelial system so that antibody-coated plateletsare no longer recognized and removed from circulation; de-creasing anti-platelet antibody production; interaction withputative immune complexes, thus preventing them fromparticipating in platelet removal by the reticuloendothelialsystem; coating platelets with a nonspecific immunoglobu-lin that hinders attachment of an intrinsically produced IgGthat causes platelet removal from circulation, and interfer-ence with macrophage Fc-receptor-mediated immune clear-ance. In contrast to i.v. IgG, there are fewer data regardingadditional immunomodulatory effects of anti-D therapy.

Bussel et al. (14) reported no significant changes in sur-face expression of FcRI, FcRII, and FcRIII on neutrophilsand monocytes following anti-D administration. They alsoreported lower monocyte FcRI expression in patients withhigh platelet response. Anti-D may have additional effectson the immune system, but the primary mechanism of ac-tion of anti-D therapy for AITP is RES blockade.

We previously compared response to anti-D (IgG)-coated RBCs and i.v. anti-D in individual patients withgood responses (21,22). The following is an evaluation ofour experience in treating FcR blockade in patients withchronic refractory ITP with anti-D (IgG)-coated RBCs. Weemployed anti-D (IgG)-coated RBCs because although i.v.anti-D was not available in Mexico (19,20), we observed fa-vorable responses in 69.8% of patients.

When maintenance with anti-D (IgG)-coated RBCs wasused, splenectomized patients experienced significant de-crease in monocyte FcR expression and increase in clear-ance rate of autologous erythrocytes treated with anti-D(IgG) and

99m

Tc-labeled RBCs (21). Differences betweenhomozygous and heterozygous Rh(D)-positive patients (Rh/Hrphenotypes) appear to have an influence in early treatmentresponse, probably due to number of antigenic sites onerythrocytes and consequent increase of RBC-bound IgGlevels. However, we found no statistical differences in ho-mozygous and heterozygous Rh(D)-positive patients theseresults were previously published by Smith et al. (23).

Scaradou et al. (24) reported results of i.v. anti-D therapyin 272 patients with chronic ITP (11 previously splenecto-mized). Approximately 50% of treated patients increased

platelet count to

�

50

�

10

9

/L. Previously splenectomizedpatients had minimal or no response to this treatment.

Our results demonstrated the effectiveness of anti-D(IgG)-coated RBCs in patients with splenectomized refrac-tory ITP. We strongly suggest that the macrophage (RES)-blockage theory is correct. Nevertheless, we acknowledgethat antiidiotypic effect, increase of plasma levels of IL-6,IL-8, and tumor necrosis factor alpha (TNF

�

), induction ofinterleukin-1 receptor antagonist (IL-1Ra), and soluble TNFreceptors (sTNFRs) release might still be important for thetherapeutic effect of i.v. immunoglobulins (18,22). Ruíz-Argüelles et al. (25) recently compared the usual dose of i.v.IgG 2 g/kg with anti-D coated RBC 50

�

g/kg in treating re-fractory ATP patients. They suggested that approximate costsof these treatments in Mexico for an adult patient weighing60 kg are as follows: for i.v. IgG: $8,400 U.S. dollars (USD)(Grifols) or 30,000 USD (Sandoz); for i.v. anti-D: $3,200USD (Cangene-Nabi), and for anti-D-coated RBC: $170USD (Cutter). As results indicate, treatment with anti-D-coated RBCs is 50–150 times less expensive than treat-ment with i.v. IgG. These data suggest that

ex vivo

anti-Dopsonized RBC may be a substantially less expensivemethod for attaining Fc-receptor blockade as part of treat-ment of patients with chronic refractory IPT.

References

1. George JN, Raskob GE. Idiopathic thrombocytopenia purpura: a con-cise summary of the pathophysiology and diagnosis in children andadults. Semin Hematol 1998;36:5–8.

2. Harrington WJ, Sprague CC, Minnich V. Immunological mechanismsin idiopathic and neonatal thrombocytopenic purpura. Ann Intern Med1953;38:433–469.

3. Shulman NR, Marder VJ, Weinrach RS. Similarities between knownantiplatelet antibodies and the factor responsible for thrombocytopeniain idiopathic purpura: physiologic, serologic, and isotopic studies. AnnN Y Acad Sci 1965;124:499–542.

4. McMillan R. The pathogenesis of chronic immune (idiopathic) throm-bocytopenic purpura. Semin Hematol 2000;37:5–9.

5. Pizzuto J, Ambríz R. Therapeutic experience on 934 adults with idio-pathic thrombocytopenic purpura: multicentric trial of the CooperativeLatin American Group on Hemostasis and Thrombosis. Blood 1984;64:1179–1183.

6. Kelton JG, Bussel JB. Idiopathic immune thrombocytopenic purpura.An update. Semin Hematol 2000;37:219–221.

7. Bussel JB. Recent advances in the treatment of idiopathic thrombocy-topenic purpura: the anti-D clinical experience. Semin Hematol 1998;36:1–4.

8. Bussel JB. Fc receptor blockade and immune thrombocytopenic pur-pura. Semin Hematol 2000;37:261–266.

9. Salama A, Kiefel V, Amberg R, Müeller-Eckhardt C. Treatment of au-toimmune thrombocytopenic purpura with rhesus antibodies (anti-RhO [D]). Blut 1984;49:29–35.

10. Salama A, Kiefel V, Müeller-Eckhardt C. Effect of IgG anti-Rho(D) inadult patients with chronic autoimmune thrombocytopenia. Am J He-matol 1986;22:241–250.

11. Baglin TP, Smith MP, Boughton BJ. Rapid and complete response ofimmune thrombocytopenic purpura to a single injection of rhesus anti-D immunoglobulin. Lancet 1986;1:1329–1330.

12. Panzer S, Grumayer ER, Haas OA, Niesner H, Graninger W. Efficacy

540

Ambriz-Fernández et al./ Archives of Medical Research 33 (2002) 536–540

of rhesus antibodies (Anti-Rho (D) in autoimmune thrombocytopenia:correlation with response to high dose IgG and the degree of haemoly-sis. Blut 1986;52:117–121.

13. Gabra GS, Mitchell R. Anti-D immunoglobulin and immune thromb-ocytopenia— a problem of ethics in blood transfusion practice. VoxSang 1988;54:246–248.

14. Bussel JB, Graziano JN, Kimberly RP, Pahwa S, Aledort L. Intrave-nous anti-D treatment of immune thrombocytopenic purpura: analysisof efficacy, toxicity and mechanism of effect. Blood 1991;77:1884–1893.

15. Ware RE, Zimmerman SA. Anti-D: mechanisms of action. Semin He-matol 1998;36:14–22.

16. George JN, El-Harake MA, Aster R. Thrombocytopenia due to en-hanced platelet destruction by immunologic mechanisms. Williamshematology. 5th ed. New York: McGraw-Hill, Inc.;1995. pp. 1315–1355.

17. Ruíz-Argüelles GJ, Apreza MMG, Pérez-Romano B, Ruíz-ArgüellesG. The infusion of anti-Rho (D) opsonized erythrocytes may be usefulin the treatment of patients, splenectomized or not, with chronic, re-fractory autoimmune thrombocytopenic purpura. A prospective study.Am J Hematol 1993;43:72–73.

18. Ambríz R, Pizzuto J, Morales M, Muñoz R, Quintanar G, García E.Treatment of chronic ITP with opsonized erythrocytes with rhesus an-tibody and labeled with Tc-99m (radioimmune method). Blood1984;n64(Suppl):233.

19. Ambríz R, Muñoz R, Quintanar E, Sigler L, Avilés A, Pizzuto J. Ac-

cessory spleen compromising response to splenectomy for idiopathicthrombocytopenic purpura. Radiology 1985;155:793–796.

20. Ambríz R, Muñoz R, Quintanar E, Sigler L, Avilés A, Pizzuto J. Ac-cessory spleen compromising response to splenectomy for idiopathicthrombocytopenic purpura. In: The year book of nuclear medicine.Chicago, IL, USA: Year Book Medical Publishers, Inc.;1987. pp. 326–327.

21. Ambríz R, Muñoz R, Pizzuto J, Quintanar E, Morales M, Avilés A. Low-dose autologous

in vitro

opsonized erythrocytes. Radioimmune methodand autologous opsonized erythrocytes for refractory autoimmune throm-bocytopenic purpura in adults. Arch Intern Med 1987;147: 105–108.

22. Mollison PL, Engelfriet CP, Contreras M. The transfusion of platelets,leukocytes and plasma components. Injections of immunoglobulin. In:Blood transfusion in clinical medicine. 9th ed. London: Blackwell Sci-entific Publications;1993. pp. 673–674.

23. Smith NA, Boughton BJ. The treatment of autoimmune thrombocy-topenic purpura with anti-D immunoglobulin: similar platelet re-sponses in homozygous and heterozygous Rh(D) positive patients.Transfus Med 1991;1:183–185.

24. Scaradavou A, Woo B, Woloski BM. Intravenous anti-D treatment ofimmune thrombocytopenic purpura experience in 272 patients. Blood1997;89:2689–2700.

25. Ruíz-Argüelles G, López-Martínez B, Flores-Martínez J, Ruíz-Argüelles A, Pérez-Romano B. An affordable Fc-receptor blockademethod to treat patients with chronic refractory autoimmune thromb-ocytopenic purpura. Haematologica 2001;86:552–553.