ABO AND GENTETICS History of the ABO system

ABO AND GENTETICS

History of the ABO system �Karl Landsteiner is the father of what we know as Blood banking. �He discovered the ABO blood groups in 1900 by observing the red cells of some individuals were clumped (agglutination) by the serum of others �Later a fourth group AB was discovered by a couple of his students. �Landsteiner also discovered that a person’s serum contained antibodies against an antigen absent from his own cells

Landsteiner won the Nobel prize in 1930 for his discovery of the ABO blood group that resulted in the saving of hundreds of lives

Two types of Antibodies �Alloantibodies: These are antibodies that are formed due to the exposure of a foreign antigen. �They are also called immune antibodies. �They are usually Ig. G �These are referred as unexpected antibodies �Isoantibodies : These are environmentally acquired, formed naturally �Substances very similar to RBC group antigens A and B are so widely distributed in nature that the antibody will develop in a person if the antigen is not present. �They are usually Ig. M �Routinely used for ABO test confirmations �Babies begin to develop these antibodies at 3 -4 months

GENETICS �Genetics is simple the study of heredity �Every trait found in your body is there because of a genetic code �DNA is the copy of your genetic code and contains the program for all functions of the human body �DNA is organized into a larger units called genes, this helps to facilitate the cells reproduction �Each gene is a segment of DNA containing the code for one particular genetic trait �There about 40, 000 individual genes in the human genetic code

GENTICS ‘CONT �The genes are still to large to duplicate accurately, so they are further grouped in units called chromosomes �The chromosome is the largest unit of the genetic code, each is a functional grouping of several hundred related genes �There are 46 human chromosomes, 23 are inherited from each parent, 22 pairs of autosomes and two sex chromosomes �With the genetic code condensed into 46 larger units, the cell finds it much easier to duplicate.

HEREDITY �Do you look like your father or your mother? �Can two brown-eyed parents have a blue-eyed child? �The gene for eye color donated from one parent may be different that the gene donated from the other parent, however, these genes will be located in the same position on the chromosomes �The position on a chromosomes occupied by a gene is called a locus �Two genes for the same trait on opposite chromosomes are called alleles �When they are same the are homozygous, when different they are heterozygous �However both genes may not be expressed

Gene Expression �Gene expression is simply the trait that is physically evident �The likelihood of a particular gene being expressed is a function of the gene’s dominance or recessiveness �This is not a factor with homozygous genes �If the genes are heterozygous then both genes may or may not be expressed depending on the dominance or recessiveness of the genes �A gene that is present on the chromosome but not expressed is called recessive �When neither gene is dominant, and both are expressed, they are called co-dominant

GENOTYPE/PHENOTYPE �The genes actually present on the chromosome make up a person’s genotype (These cannot be tested for in the blood bank) �The gene that is actually physically expressed is called the phenotype ( and can be tested for in the lab) �Understanding genotype and phenotype will help us to answer the blue-eyed question

Our blue eyed child

ABO System �There are four ABO blood types determined by three inherited genes A, B and O �There also variants of the A and B genes which give rise to subgroups of the A and B antigens �A and B genes are dominant over the O gene and express themselves as detectable antigens on the red blood cells �The O gene does not cause the production of an O antigen

There are six different Genotypes but only four Phenotypes Genotypes AA AO BB BO AB OO Phenotypes A (AA, AO) B (BB, BO) AB (AB) O(OO)

ABO Antigen Detection �Detected using Known monoclonal antibodies �Specific under the manufacturer's recommended test conditions �Must have sufficient tier �Must be sterile, clear, in a container with a dropper and stable �Should be marked with an expiration date �Stored at 40 C �Exact requirements are defined by the FDA Center for Biologics Evaluation and Research (CBER)

Test �If the Dad is type O and the Mom is Type AB, what percentage of the children will be Type O?

Incidence of ABO groups � ABO Group European African Asia Hispanic �O 44 49 43 55 �A 43 27 27 28 �B 9 20 25 13 �AB 4 4 5 4 �About 80% of group A and AB have the A 1 gene. Most of the other 20% are A 2 or A 2 B �Subgroups of B are extremely rare

Laboratory Testing �Forward Type: Antigen is identified by combining the unknown (Patient or donor) red blood cells with known antibody (Anti-A or Anti-B) �Reverse Type: The presence of antibody is identified by combining the unknown (patient or donor) with know ABO red blood cells (A 1 or B) �Agglutination is seen as the positive result �An ABO discrepancy occurs when the results of the forward and reverse type do not correlate.

ABO Discrepancy �Further testing is always required, past history checked and check strength of reactions! �Weaker reactions are more likely to be aberrant than stronger reactions and reverse discrepancies are more common than in the forward type. �Possible causes: �ABO subgroups �Transfusion/Transplantation �Age (older or younger) �Probiotics (increase in Anti-A) �Treatments (immunosupression) �Cold reactive antibody �Patient/Sample identification error during collection �Rouleaux, excess protein

Test �You determine that a patient’s antibody screen in negative, You have the following ABO testing results: �Anti-A Anti-B Anti-D A 1 cell B cell 4+ 0 4+ 1+ 4+ Your repeat ABO results match the original results Into which category of ABO discrepancy does this sample likely fit? a. Missing or weak reaction in the reverse type b. Missing or weak reaction in the forward type c. Unexpected positive reaction in the forward type d. Unexpected positive reaction in the forward type What are some possible causes for these results?