Characteristics of HTLA antibodies include:

  • IgG immunoglobulins
  • Usually of high titre but low avidity for the corresponding antigen, therefore reactions are weak
  • Variable reactions with adult red cells
  • Weaker or negative reactions with cord red cells Weaker or negative reactions with enzyme-treated red cells (some)
  • Difficult to adsorb and elute

The apparent low avidity of HTLA antibodies may relate more to the low number of antigen sites on the red cells than to the binding constant of the antibody.

Because most of the antibodies formerly characterized as HTLA (due to serologic characteristics) have now been assigned to independent blood group systems, HTLA is becoming less used as a term to describe them.