ANTIGENIC FACTORS INHERITED IN THE SERUM

ANTIGENIC FACTORS INHERITED IN THE SERUM

HAPTOGLOBINS (Hp) –

Haptoglobins are haemoglobin binding proteins which are present in human serum. Their genotypes are Hp1Hp1, Hp2Hp1 and Hp2Hp2. The different types of haptoglobins can be identified from different characteristic bands produced by analysis of human serum by gel electrophoresis. Haptoglobin is generally absent in the serum of a newborn infant. But by 6 months of age, most infants (97%) have it. Haptoglobins have immense value in paternity determination. It can add 6.29% to the exclusion value achieved by the other methods and it itself has 18.07% exclusion capacity.

ANTIGENIC FACTORS INHERITED IN THE SERUMIn starch gel electrophoresis, Hp 1-1 shows a band, a little behind the band for haemoglobin. Hp 2-2 develops slow moving bands. Hp 2-1 bands have intermediate mobility.

Gm FACTORS IN BLOOD SERUM

Gm 1 antigen is present in the serum of 60% of Europeans. Gm (1, 5) is present in all Africans. Their presence is detected by Gr. O D +ve cells sensitized by incomplete anti – D serum and agglutinated by anti — Gm serum.

THE RED CELL ENZYME SYSTEM FOR IDENTIFICATION PURPOSES

A good many enzymes of the R.B.C.s show inherited variations which can be detected by starch gel electrophoresis test at 4°C, carried on over rather a long period, followed by subsequent application of a reaction mixture. Examples of these enzymes are phosphoglucomutase (PHM), red cell acid phosphatase (AP), Adenosene deaminase (ADA) and adenylate kinase (AK).

In the PGM system PGM1 and PGM2 are known which may give phenotype pattern of PGM 1 – 1, PGM2-1 and PGM2-2 PGM1-1 is most frequent (about 56%).

Exclusion of paternity

If at any stage of blood group investigations, the putative father shows presence or absence of some group factor or red cell enzyme factor which, giving due consideration to the blood group and enzyme factors present in the mother, show incompatibility with those of the child, then, that conclusively rules him out to be the father of the child and the dispute is settled. The chance of exclusion increases for non-fathers, when more and more blood group and other relevant tests are performed.

Paternity exclusion chances with different blood group tests
Grouping system exclusion rate for each system cumulative exclusion rate
ABO 17.6% 17.6%
MNSs 32.05% 44.01%
Rh 28.00% 59.68%
Kell 3.34% 61.08%
Duffy 4.81% 62.95%
Lutheran 3.33% 64.18%
Kidd 2.86% 65.2%
Hp 18.07% 71.49%
Gc 15.86% 76.01%
Gm(1) 6.47% 77.56%
Ag 14.22% 80.75%
PGM 15.32% 83.70%
AK 4.20% 84.38%

On the other hand, performance of more and more tests with similarity in the groups of putative father and child, increases the force in the suggestion that the putative father may actually be the father of the child in question. The defendant lawyer may take the plea of the fact that, with the present knowledge and practice about 15% non-fathers can not be excluded as yet. While putting or facing such an argument, it should be remembered that, the force of the suggestion of the person’s being the father is increased, if we take into consideration that, the mother of the child, while pointing him as the father of the child, did not have any idea about his blood group patterns and that the mother has pointed to such a person whose blood examination also strongly suggests that he could be the father of the child.

Inheritance of Haemoglobin variants also may help paternity determination.