Serological tests: good –ve tests, they include:

1. Typing of blood group systems: They are red cell surface antigens that are permanent throughout life except some temporary changes after blood transfusion, so don’t do blood grouping except after at least 3 months post-transfusion.

They include:

1. ABH system:
1. There are 3 antigens (A,B,H) giving 4 phenotypes (A, B, AB, O) and 6 genotypes (AA, AO, BB, BO, AB, OO) as every individual has two genes on each chromosome. ABO system locus is located on chromosome 9.
2. Other blood group systems:

• RH system: It is present in 85-90% of persons hence they are expressed as Rh +ve, the remaining are Rh -ve. Their specific locus is located on chromosome 1. There are 6 antigens (C,c, D,d, E,e). RH+ve type should have at least one of (C or D or E). The most important is D antigen. RH-ve type don’t have these antigens.

• MN system: These are 3 groups M, N and MN and are present at birth. They are inherited as a Mandelian dominant so M or N does not appear in blood of child unless present in one parent at least. There are 2 antigens (M&N) giving 3 phenotypes (M, N, MN), 3 genotypes (MM, NN, MN). Ss and MN are closely linked but separate gene loci on chromosome 4. Several instances of recombination between the loci have been observed. They are 4 antigens (M, N, S, s) giving 9 phenotypes (MS, MSs, Ms, NS, NSs, Ns, MNS, MNSs, MNs).

• Kell (K) system. There are 2 antigens (K, k) giving 3 genotypes (KK, Kk, kk).
• Duffy system: Two antigens (Fya, Fyb) giving 3 genotypes (Fya+b+, Fya+b- & Fya-b+). Fya-b- type is found in black people (lacking both antigens)
• Kidd system: There are 2 antigens (JKa, JKb) giving 3 genotypes (JKa+b+, JKa+b-, JKa-b+).

2. Typing of red cell isoenzymes:

They are a group of enzymes present inside RBCs which catalyze various vital biochemical reactions. They show polymorphism i.e. they are present in different forms in different people hence the term isoenzymes. e.g:

• Phosphoglucomutase (PGM): It is located on chromosome 1. Two antigens (PGM1, PGM2) giving 3 genotypes (PGM1, PGM2 & PGM2-1).

• Adenylate kinase (AK): has 3 genotypes (AK1, AK2 & AK2-1).

• Acid phosphatase (AP).
• Estrase D
• Glutamate pyruvate transaminase (GPT).
• 6 phosphogluconate dehydrogenase (6 PGD).
• Carbonic anhydrase (CA).

3. Typing of serum protein systems e.g.:

• Haptaglobins: Two antigens (HP1, HP2) giving 3 genotypes (HP1-1, HP 2-2 & HP 2-1).

• Group specific components (GC): Two antigens (GC1, GC2) giving 3 genotypes (GC1, GC2 & GC1-2).

• Transferrin (Tf)

• Protease inhibitor (PI).

• Immunoglobulin markers (Gm, Km).

• The third component (C3)
  

• Protease inhibitors as > antitrypsin

4. Typing of hemoglobin:

• Fetal hemoglobin (HbF) present in the fetus and very young infants.

• Sickle cell hemoglobin (HbS) which is responsible for sickle cell anemia, it is almost exclusively present in blacks and Hispanic people.

• HbC: normally present in black people, less frequently in Hispanic people, never in other ethnic groups.
  

• Hb D, E, A (adult Hb).

5. HLA typing (Human leucocyte antigens or complex)

• This system consists of protein substances (about 50 antigens) on the surface of all cells including leucocytes on which they were first discovered.
• HLA- A, B, C, D, DR and DQ constitute the major human leucocyte antigens i.e. major histocompatibility complex (MHC) which is related to immunity. It has been assigned to the short arm of chromosome 6.

Category: Forensic Medicine Notes