Absorption-Inhibition
Definition
A known volume of antiserum is exposed to the stain; the residual unbound antibody is then titrated against indicator cells. A drop in titre points to the antigen present.
- Step 1
- Known antiserum volume exposed to the stain
- Step 2
- Residual unbound antibody titrated against indicator cells
- Positive result
- A drop in titre
- Field
- Bloodstain ABO grouping
Common questions
Why does a titre drop indicate the antigen is present?+
The stain's antigen binds and removes antibody from the antiserum, leaving less free antibody available to agglutinate the indicator cells in the later titration step.
Is this method still used in current casework?+
Rarely. DNA-based STR or SNP typing has largely replaced serological absorption-inhibition for identifying bloodstains, though the method still appears in review of older cases.
What can cause a false negative result?+
A degraded or very small stain may not carry enough antigen to bind a measurable amount of antibody, so the titre fails to drop even though the antigen is genuinely present.
Related terms
- Absorption-Elution
- A technique for detecting antigens on dried red cell debris. Specific antiserum is absorbed onto the stain; if the antigen is present,...
- Agglutination
- Clumping of red cells that occurs when antibodies in serum bind to incompatible antigens on the cell surface, cross-linking cells into visible...
- Antiserum
- Serum collected from an immunised animal containing antibodies directed against a specific antigen or group of antigens. In species identification, antiserum raised...
- Lattes Crust Method
- Classical direct agglutination. A crumb of the dried crust is teased into a drop of known antiserum on a slide. Leone Lattes,...
- Mixed Agglutination
- A microscopy-based technique in which indicator cells form rosette aggregates around antigen-bearing stain material via antibody bridges. Positive results are read as...
- Secretor Status
- A genetic trait that determines whether a person expresses their ABO blood group antigens in secreted body fluids such as saliva, semen,...
- Sensitivity Threshold
- The smallest stain on which a technique still gives a reliable read. The key axis for choosing between Lattes, inhibition, elution and...