**7. Causes of haemolytic transfusion reactions**

#### **7.1 Haemolytic transfusion reactions caused by alloantibodies**

The most common cause of haemolytic transfusion reactions is the immunological destruction of red blood cells resulting from the reaction of antibodies in the recipient's blood and the antigens present on the transfused donor's blood cells to which these antibodies are made.

Antibodies capable of destroying transfused blood cells are called clinically relevant antibodies, and the transfusion reaction in the event of immunological incompatibility depends on: (1) specificity of antibodies; (2) thermal amplitude of the antibodies; (3) IgG classes and IgG subclasses; (4) number, density and spatial configuration of antigenic sites on red blood cells; (5) the ability of antibodies to activate the complement system; (6) plasma concentrations of antibodies and (7) volumes of transfused red blood cells. A very important feature of all antibodies responsible for causing a haemolytic transfusion reaction is its in vitro activity at 37°C.

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**Table 4.**

*Post-Transfusion Haemolytic Reactions DOI: http://dx.doi.org/10.5772/intechopen.91019*

amplitude of up to 37°C.

**Blood group system**

Lewis Anti-Lea

Vel Anti-Vel

Antibodies detected at a lower temperature are not considered clinically relevant, for example, anti-A1, anti-M and anti-P1, whose optimal reaction is usually at low temperature, but if detected at 37°C, they can cause destruction of red blood

Features of antibodies (specificity, class and heat amplitude) and antigens (density of antigenic sites and their distribution) against which the antibodies directed are interconnected. In different people, antibodies with a particular specificity most often occur in the same class of immunoglobulins and have a similar heat amplitude, for example, anti-A, anti-B and anti-AB from the ABO system often belong to both IgM and IgG classes, they bind complement and have an extended thermal

A and B antigens are highly immunogenic. Anti-A, anti-B and anti-AB antibodies are involved in causing an early intravascular transfusion reaction, and transfusion of incompatible blood in the ABO system poses a threat to the recipient's life, especially when group A red blood cells are transfused to a patient with group O. Sixty-one (61%) of all haemolytic transfusion-related fatal reactions are associated with the ABO incompatibility [38, 39]. A contrasting example is the Lua antigen and anti-Lua antibodies. They are usually IgM molecules, are rarely active at 37°C and usually do not bind complement. Lua antigens have uneven distribution on red blood cells and are weakly immunogenic. No cases of acute haemolytic reaction caused by anti-Lua antibodies have been reported, delayed transfusion

Not all detectable alloantibodies that react with red blood cells can cause a haemolytic reaction. The specificity of the antibodies potentially responsible for

anti-Vel. Other antibodies cause intravascular haemolysis, but sometimes they may be accompanied by intravascular haemolysis. Such reactions were observed in the following blood group systems: Rh, MNSs, Lutheran, Kell, Duffy, Diego and Lewis. The mechanism of appearance of intravascular symptoms has not been fully explained, because although some of the antibodies bind complement components,

**Intravascular haemolysis Extravascular** 

, anti-P1 and

**haemolysis**

, -Jkb , -Jk3

, -Fyb

, -Dob

haemolytic reaction is rare and occurs only in mild form.

ABO, H Anti-A, -B, -AB, -H in the Bombay phenotype

Rh All Kell Anti-K All Kidd Anti-Jka Anti-Jka

Duffy Anti-Fya

Cartwright Anti-Yta

Colton Anti-Coa Dombrock Anti-Doa

*Specificity of selected antibodies associated with haemolytic transfusion reactions.*

MNS Anti-M, -S, -s, -U Lutheran Anti-Lub

intravascular and extravascular haemolysis is shown in **Table 4**. Similar reactions to anti-A and anti-B come from anti-PP1Pk

cells with the appropriate antigen. They then become clinically significant.

#### *Post-Transfusion Haemolytic Reactions DOI: http://dx.doi.org/10.5772/intechopen.91019*

*Human Blood Group Systems and Haemoglobinopathies*

**Initial symptoms of haemolytic transfusion** 

*Initial symptoms of haemolytic transfusion reactions.*

**reactions**

Dark urine

Ache Dyspnoea

Ache Dyspnoea

**Table 3.**

**Intravascular haemolysis** Nausea or vomiting

**Extravascular haemolysis** Fever and/or chills Nausea or vomiting

Decrease in RR and/or tachycardia

threatens the patient's life.

which these antibodies are made.

[37]. Clinical manifestations are shown in **Table 3**.

**7. Causes of haemolytic transfusion reactions**

**7.1 Haemolytic transfusion reactions caused by alloantibodies**

accompanied by anaemia. In both cases, the patient's serum bilirubin increases, but it depends on the degree of haemolysis as well as liver function [1]. Elevated LDH is always observed with intravascular haemolysis, not always with extravascular haemolysis. Reduced haptoglobin levels usually occur in both types of haemolysis. Drop in blood pressure is much more common in patients with intravascular than extravascular haemolysis. Renal failure and DIC are also more commonly associated with intravascular haemolysis. Some patients may experience organ failure such as the pancreas, heart and even multiple organ failure that

**Complications**

Kidney failure

Kidney failure

Disseminated intravascular coagulation (DIC)

disseminated intravascular coagulation (DIC)

In unconscious patients and patients under general anaesthesia, it may be difficult to recognise a haemolytic transfusion reaction, as some symptoms may go unnoticed (e.g. pain and nausea). Pain, which is described as a symptom of haemolytic reactions, is located at the puncture site, back, chest, groin and head. The occurrence of pain in the haemolytic transfusion reaction is not clear. It is probably the result of direct stimulation of nociceptive nerves in perivascular tissue by bradykinin, which, in turn, is released during sudden activation of complement

The most common cause of haemolytic transfusion reactions is the immunological destruction of red blood cells resulting from the reaction of antibodies in the recipient's blood and the antigens present on the transfused donor's blood cells to

Antibodies capable of destroying transfused blood cells are called clinically relevant antibodies, and the transfusion reaction in the event of immunological incompatibility depends on: (1) specificity of antibodies; (2) thermal amplitude of the antibodies; (3) IgG classes and IgG subclasses; (4) number, density and spatial configuration of antigenic sites on red blood cells; (5) the ability of antibodies to activate the complement system; (6) plasma concentrations of antibodies and (7) volumes of transfused red blood cells. A very important feature of all antibodies responsible for causing a haemolytic transfusion reaction is its in vitro

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activity at 37°C.

Antibodies detected at a lower temperature are not considered clinically relevant, for example, anti-A1, anti-M and anti-P1, whose optimal reaction is usually at low temperature, but if detected at 37°C, they can cause destruction of red blood cells with the appropriate antigen. They then become clinically significant.

Features of antibodies (specificity, class and heat amplitude) and antigens (density of antigenic sites and their distribution) against which the antibodies directed are interconnected. In different people, antibodies with a particular specificity most often occur in the same class of immunoglobulins and have a similar heat amplitude, for example, anti-A, anti-B and anti-AB from the ABO system often belong to both IgM and IgG classes, they bind complement and have an extended thermal amplitude of up to 37°C.

A and B antigens are highly immunogenic. Anti-A, anti-B and anti-AB antibodies are involved in causing an early intravascular transfusion reaction, and transfusion of incompatible blood in the ABO system poses a threat to the recipient's life, especially when group A red blood cells are transfused to a patient with group O. Sixty-one (61%) of all haemolytic transfusion-related fatal reactions are associated with the ABO incompatibility [38, 39]. A contrasting example is the Lua antigen and anti-Lua antibodies. They are usually IgM molecules, are rarely active at 37°C and usually do not bind complement. Lua antigens have uneven distribution on red blood cells and are weakly immunogenic. No cases of acute haemolytic reaction caused by anti-Lua antibodies have been reported, delayed transfusion haemolytic reaction is rare and occurs only in mild form.

Not all detectable alloantibodies that react with red blood cells can cause a haemolytic reaction. The specificity of the antibodies potentially responsible for intravascular and extravascular haemolysis is shown in **Table 4**.

Similar reactions to anti-A and anti-B come from anti-PP1Pk , anti-P1 and anti-Vel. Other antibodies cause intravascular haemolysis, but sometimes they may be accompanied by intravascular haemolysis. Such reactions were observed in the following blood group systems: Rh, MNSs, Lutheran, Kell, Duffy, Diego and Lewis. The mechanism of appearance of intravascular symptoms has not been fully explained, because although some of the antibodies bind complement components,


#### **Table 4.**

*Specificity of selected antibodies associated with haemolytic transfusion reactions.*

their reactions end with C3 components. Only in the case of rare haemolytic reactions due to anti-Lea it was shown that the coated cells are destroyed by the spleen macrophages very slowly and in the event of transfusion of large volumes of red blood cells, they become inefficient. Then intravascular haemolysis coincides with visible haemoglobinuria [40, 41]. Interesting clinical point of view are antibodies from the Kidd system. They activate the complement system to the stage of binding of the C3b component, causing extravascular haemolysis. However, the symptoms in some recipients, or the occurrence of a reaction already during a blood transfusion and haemoglobinuria, indicate that the destruction of blood cells also takes place inside the vessel. In the laboratory setting, anti-Jka antibodies are called "insidious" antibodies because they are often difficult to detect due to their low concentration, and yet they can cause a severe haemolytic complication [41].

Patients with antibodies found to be clinically insignificant may theoretically be given a blood transfusion from a donor with the antigen to which they are directed. In clinical practice, however, such antibodies can sometimes destroy donor blood cells. Therefore, if possible, blood without this antigen should be selected [41].

Another cause for haemolytic transfusion reaction may be a secondary immune response in patients who have developed alloantibodies during previous transfusions of blood components or pregnancy. This is called delayed haemolytic transfusion reaction (DHTR) in which current blood transfusion stimulates memory lymphocytes and stimulates the production of alloantibodies directed at incompatible antigen found on transfused blood cells [21, 42]. In approximately 50% of cases, alloantibodies produced after transfusion or pregnancy cease to be detected after a few months, and this period of time depends on the specificity of the antibodies and the individual characteristics of the immune system. Schonewille et al. found that, using current laboratory methods, 25% of red blood cell antibodies become indeterminate on average after about 10 months from production [43]. Therefore, pre-transfusion tests may not always detect the presence of antibodies. Antibodies stimulated for synthesis may cause symptoms of haemolysis after 3–10 days, usually very mild and their presence can be detected after 10–21 days. **Table 5** presents features of delayed haemolytic transfusion reaction and the time of their occurrence.

Antibodies that cause a delayed haemolytic transfusion reaction are IgG molecules that are binding or non-binding for complementary components. Their specificity is most often directed to the antigens of the Rh, Kidd, Duffy, MNS and Kell systems [14]. In approximately 11% of cases, more than one antibody specificity is


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*Post-Transfusion Haemolytic Reactions DOI: http://dx.doi.org/10.5772/intechopen.91019*

incompatible platelets [48–50, 53].

occurs in high-dose IVIG recipients [55].

detected. In rare cases, the result of transfusion alloimmunity in DHTR may be the production of autoantibodies (warm IgG autoantibodies or cold autoagglutinins).

This phenomenon occurs in patients with sickle cell disease [44–46].

**7.2 Haemolytic transfusion reactions due to passive transmission of alloantibodies in blood components or in blood products**

Transfusion of plasma, platelet or granulocyte concentrate from donors incompatible in the ABO system with the recipient may lead to acute haemolytic transfusion reaction and even death. The severity of the reaction depends on the titre of anti-A and/or anti-B antibodies in the transfused plasma or in the blood component containing the plasma, and on its volume [47–49]. Tests on the ABO system titre in group O apheresis concentrates of platelets show that 26% of samples have an anti-A or anti-A, B antibody titre of 64 or higher. This concentration may be responsible for causing a haemolytic reaction [50]. In turn, the results of studies by Coolig et al. [51] carried out in pooled platelet concentrates of whole blood groups showed that 60% of them had anti-A titres of at least 64 [51]. Repeated transfusions of ABO incompatible platelet concentrate may lead to accumulation of anti-A antibodies in the recipient's plasma, which may result in severe haemolytic reactions [52]. Unfortunately, despite many studies, it has not been possible to determine the critical titre of anti-A and/or anti-B antibodies that would be safe in the event of transfusion of ABO incompatible platelet concentrates, and in many countries, proprietary haemolysis prevention programs have been developed for recipients of

Haemolytic transfusion reactions due to passively transferred anti-A and/or anti-B antibodies have also been observed in patients after intravenous immunoglobulin administration [54]. Spath et al. [55] analysed reports available in the literature describing cases of haemolysis in patients treated with intravenous immunoglobulins [55]. They showed that the haemolytic reaction is induced by IgG anti-A/B antibodies present in immunoglobulin products. The reaction generally

**7.3 Haemolytic reaction associated with the "bystander immune cytolysis"**

than the reactions of antibodies in the recipient's blood and the antigen present on the donor's blood cells. This additional mechanism occurs when recipient's red blood cells are destroyed by a reaction called "bystander immune cytolysis". It is defined as the immunological destruction of red blood cells by antibodies whose specificity corresponds to antigens found on other cells/blood cells (e.g. HLA antigens found on leukocytes and plasma proteins), while red blood cells are only close to this immunological "confusion" [56]. They are destroyed by the complement system, although they did not participate directly in the antigen-antibody reaction. One of the reasons for this haemolytic reaction is the binding of the C567 complement complex, activated in an immune reaction, to the membrane of red blood cells not participating in the reaction but located in the vicinity [56]. Blood cells are destroyed as a result of the activation of the binding of the remaining components of C8 and C9 complement and the formation of the MAC complex on the blood cells [56]. The mechanism of "bystander" haemolysis is similar to the destruction of blood cells in patients with paroxysmal nocturnal haemoglobinuria [57, 58]. A characteristic feature of the cell membrane of these blood cells is the lack or weak expression of the CD55 (DAF) and CD 59 (MIRL) proteins, which are complement inhibitors. This makes the subject more susceptible to haemolysis. It was found that

The haemolytic transfusion reactions may have a different immunological origin

#### **Table 5.** *Features of late hemolytic transfusion reaction and time of their occurrence [21].*

*Human Blood Group Systems and Haemoglobinopathies*

their reactions end with C3 components. Only in the case of rare haemolytic reactions due to anti-Lea it was shown that the coated cells are destroyed by the spleen macrophages very slowly and in the event of transfusion of large volumes of red blood cells, they become inefficient. Then intravascular haemolysis coincides with visible haemoglobinuria [40, 41]. Interesting clinical point of view are antibodies from the Kidd system. They activate the complement system to the stage of binding of the C3b component, causing extravascular haemolysis. However, the symptoms in some recipients, or the occurrence of a reaction already during a blood transfusion and haemoglobinuria, indicate that the destruction of blood cells also takes place inside the vessel. In the laboratory setting, anti-Jka antibodies are called "insidious" antibodies because they are often difficult to detect due to their low concentration, and yet they can cause a severe haemolytic complication [41].

Patients with antibodies found to be clinically insignificant may theoretically be given a blood transfusion from a donor with the antigen to which they are directed. In clinical practice, however, such antibodies can sometimes destroy donor blood cells. Therefore, if possible, blood without this antigen should be selected [41].

Another cause for haemolytic transfusion reaction may be a secondary immune response in patients who have developed alloantibodies during previous transfusions of blood components or pregnancy. This is called delayed haemolytic transfusion reaction (DHTR) in which current blood transfusion stimulates memory lymphocytes and stimulates the production of alloantibodies directed at incompatible antigen found on transfused blood cells [21, 42]. In approximately 50% of cases, alloantibodies produced after transfusion or pregnancy cease to be detected after a few months, and this period of time depends on the specificity of the antibodies and the individual characteristics of the immune system. Schonewille et al. found that, using current laboratory methods, 25% of red blood cell antibodies become indeterminate on average after about 10 months from production [43]. Therefore, pre-transfusion tests may not always detect the presence of antibodies. Antibodies stimulated for synthesis may cause symptoms of haemolysis after 3–10 days, usually very mild and their presence can be detected after 10–21 days. **Table 5** presents features of delayed haemolytic transfusion reaction and the time of their occurrence. Antibodies that cause a delayed haemolytic transfusion reaction are IgG molecules that are binding or non-binding for complementary components. Their specificity is most often directed to the antigens of the Rh, Kidd, Duffy, MNS and Kell systems [14]. In approximately 11% of cases, more than one antibody specificity is

**Time (days) Occurrence Explanation**

1 Red blood cell transfusion

10–21 Post-transfusion testing of blood samples:

>21–300 DAT may be positive, eluate testing

panagglutination

DAT and screen of antibodies positive

may show presence of alloantibodies or

*Features of late hemolytic transfusion reaction and time of their occurrence [21].*

0 Negative pre-transfusion test Antibody titres below detection threshold

3–10 Clinical symptoms of haemolysis Acceleration of transfused blood cells

>21 DAT can be negative Destruction of donor blood cells in

destruction

Increase in antibody titre; donated blood

reticuloendothelial system and/or liver

Alloantibodies not specifically associated with autologous red blood cells or produced warm antibodies

cells coated with antibodies

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**Table 5.**

*DAT—direct antiglobulin test.*

detected. In rare cases, the result of transfusion alloimmunity in DHTR may be the production of autoantibodies (warm IgG autoantibodies or cold autoagglutinins). This phenomenon occurs in patients with sickle cell disease [44–46].
