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Immunity > Immunology of Blood Transfusion > Flashcards

Immunology of Blood Transfusion Flashcards

1
Q

Carry antigenic proteins and carbohydrates on their surfaces

A

Erythrocytes

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2
Q

Each such molecule defines a

A

Blood Group

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3
Q

The specific alleles in DNA, and the specific antigens present on rbc, define an individual=s

A

Blood Type

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4
Q

Which blood groups are the most important in blood transfusion?

A

ABO and Rh groups

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5
Q

Present in normal individuals, never exposed to foreign erythrocytes

A

Antibodies to ABO antigens

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6
Q

However, formation of anti-Rh antibodies requires exposure to

A

Rh-antigen

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7
Q

Formation of anti-Rh antibodies requires exposure to Rh antigen; preventing an immune response to them is important to prevent

A

Hemolytic Disease of the Newborn

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8
Q

Terminal sugars on oligosaccharides of glycoproteins and glycolipids of the red cell membrane

A

ABO epitopes

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9
Q

There are about one million copies of the epitope on each erythrocyte, and the oligosaccharide chains extend well away from the cell surface, so that an erythrocyte is a very good target for

A

Anti-ABO antibodies

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10
Q

The precursor of ABO antigens is

A

H substance

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11
Q

Genes of the ABO system encode enzymes which add terminal sugars to

A

H substance

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12
Q

H substance with a terminal N-acetyl galactosamine added

A

A substance

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13
Q

H substance with a terminal galactose added

A

B substance

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14
Q

Converts H substance to A substance

A

The Ia enzyme

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15
Q

Converts H substance to B substance

A

The Ib enzyme

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16
Q

The product of the Io allele is non-functional and adds nothing to

A

H substance

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17
Q

Individuals make antibodies to ABO antigens they

A

Do not possess

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18
Q

These antibodies [isohemagglutinins or isoantibodies] are usually

A

IgM

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19
Q

Their synthesis does not require exposure to foreign erythrocytes; they are made in response to similar polysaccharide structures in bacteria and plants. They are called

A

Natural Antibodies

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20
Q

People of blood types A, B, AB, or O do not make

A

Anti-H

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21
Q

People who cannot convert h to H do make

A

Anti-H antibodies

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22
Q

On routine typing these people appear as Type O since they have neither A nor B antigens. This blood type is called

A

Bombay O

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23
Q

The Bombay O type is rare in Caucasians but common in some

A

Asian populations

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24
Q

Persons of Bombay O genotype will have transfusion reactions if they receive

A

Ordinary type O

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25
Q

They can be identified because their serum anti-H antibodies agglutinate

A

Type O red cells

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26
Q

Defined by the antigens present on red cells

A

ABO blood type

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27
Q

ABO antigens are also present on endothelium and must be matched in

A

Organ transplant

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28
Q

Specifies a complex group of red-cell antigens

A

Rh system

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29
Q

By far the most important antigen is the

A

Rh0 or D antigen

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30
Q

Red cells of persons who are Rh+ have this antigen and red cells from people who are Rh- lack it

A

Rh0 or D antigen

31
Q

Antibodies to Rh antigens are formed only as a result of exposure to

A

Rh incompatible blood

32
Q

Anti-Rh antibodies are usually

A

IgG

33
Q

Anti-Rh antibodies are usually IgG; they do not activate

A

Complement

34
Q

Bind to rbc, opsonize them, and cause them to be phagocytosed and destroyed

A

Anti-Rh antibodies

35
Q

They agglutinate red cells poorly and usually cannot be detected by direct agglutination

A

Anti-Rh antibodies

36
Q

Rh incompatibility between mother and fetus can lead to

A

Fetal hemolytic disease

37
Q

An Rh-negative mother carrying an Rh-positive fetus may be exposed to small numbers of fetal red cells, either as the result of small hemorrhages in the placenta during pregnancy, or, more commonly, when the placenta separates from the

A

Uterine Wall at Birth

38
Q

She may then make

A

Anti-Rh+ antibodies

39
Q

Maternal exposure to fetal rbc can be determined by use of an immuno-fluorescent assay for

A

Hemoglobin F

40
Q

Can be detected by the Indirect Antiglobulin Test (IDAT)

A

Maternal anti-D antibodies

41
Q

Maternal immune response to Rh antigen can be prevented by administration of

A

Anti-Rh+ immune globulin (Rhogam)

42
Q

Often administered one or more times during pregnancy, without any testing if the mother is Rh- and the father Rh+

A

Rhogam

43
Q

Maternal IgG antibodies to any red cell antigen can cause

A

Fetal Hemolytic Disease

44
Q

Anti-ABO antibodies are normally IgM and do not cross the

A

Placenta

45
Q

ABO antigens are present in soluble form in plasma and are present on many cell types; thus anti-ABO IgG antibodies may be neutralized before they can damage

A

Fetal RBCs

46
Q

Maternal antibody to paternal platelet antigens can deplete fetal platelets and create a risk of

A

Fetal Hemmorhage

47
Q

Detects antibodies bound to red cells in vivo which do not agglutinate them

A

The Direct Antiglobulin Test (DAT) (Direct Coombs test)

48
Q

Tests for non-agglutinating antibodies are done under conditions that favor

-Ex: low ionic strength medium and/or addition of polyethylene glycol (PEG)

A

Antibody binding

49
Q

Detects free antibody to erythrocyte antigens

A

The Indirect Antiglobulin Test (IAT or IDAT) (Indirect Coomb’s test)

50
Q

Used in pre-transfusion testing to detect non-agglutinating antibodies in sera of blood donors and recipients

A

IDAT (indirect Coombs)

51
Q

In the case of maternal-fetal Rh incompatibility, it is used to detect anti-Rh+ antibodies in maternal serum

A

IDAT (indirect Coombs)

52
Q

In IDAT, to detect this antibody patient plasma is first mixed with erythrocytes bearing the antigen of interest; then, in a second step, we add

A

Anti-IgG antibody

53
Q

What are the two pre-transfusion tests for non-agglutinating antibodies to erythrocytes?

A

DAT and IDAT

54
Q

Determines the ABO and Rh antigens present on donor and recipient erythrocytes, and the antibodies to these antigens that are present in plasma

A

Typing

55
Q

ABO and Rh antigens are determined by agglutination of red cells with antisera for

A

A, B, and Rho(D). (A and B are sometimes referred to as isoantigens.)

56
Q

The ABO type is confirmed by mixing patient serum with know Type A and B cells to detect

A

Anti-A and anti-B antibodies

57
Q

Test results for antigens and antibodies should be consistent with each other: If erythrocytes react with anti-A but not anti-B, the

  1. ) Blood type should be?
  2. ) Serum should contain?
A
  1. ) A

2. ) Anti-B but not anti-A antibodies

58
Q

Detects anti-rbc antibodies to the many minor blood groups

A

Screening

59
Q

Allelic variation exists for many erythrocyte membrane components besides ABO and Rh. Antibodies to these are uncommon and usually

A

Non-agglutinating

60
Q

Serum of donors and recipients is screened by mixing it with members of a panel of type O red cells carrying known

A

Minor blood group antigens

61
Q

Antibodies to these antigens are detected by hemolysis or agglutination; antibodies incapable of hemolysis or agglutination are detected by the

A

IDAT

62
Q

Ensures that the actual unit of blood transfused is compatible with the patient

A

Cross-matching

63
Q

Blood is cross-matched by mixing donor cells with recipient plasma [the major cross-match]. If agglutination is not observed, non-agglutinating antibody is sought by the

A

IDAT

64
Q

May result in hemolysis, fever, chills, and low back pain, and may progress to shock, presence of free hemoglobin in blood and urine, and renal failure

A

Immediate transfusion reactions

65
Q

In a transfusion reaction, there may be decreased hematocrit or increased

A

Bilirubin

66
Q

If whole blood, rather than washed erythrocytes, is transfused, there may be reactions to

A

WBC or plasma proteins

67
Q

Delayed transfusion reactions (3-10 days after transfusion) are more common than

A

Immediate reactions

68
Q

The usual source of immediate reactions is

A

Human error

69
Q

Delayed reactions result from a immune response to

A

Minor antigens

70
Q

Antibodies to HIV do not appear until

A

1-2 months after infection

71
Q

Because of the recent epidemic, is now screened for by PCR or similar tests

A

West Nile Virus

72
Q

If the recipient is immunocompromised, blood is also screened for

A

Cytomegalovirus [CMV]

73
Q

Serologic screening is impractical, screening relies on a history taken at the time of donation

A

Plasmodium [the cause of malaria] and Babesia

74
Q

There is no immune response to

A

Bovine spongiform encephalopathy (mad cow disease)

Immunity (33 decks)

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