Is H antigen considered as an agglutinogen?
H antigen is a precursor for A and B antigens, and hh (recessive) individuals do not express this antigen. See Bombay blood group. This is an example of epistasis. Since H antigen is present in all A,B,AB and O blood groups, transfusion from any of these to an hh individual will cause a haemolytic reaction. Anti-H antibodies are agglutinins and have been referred to as agglutinins in the scientific literature. 


  The fairly strong anti-H agglutinins present in 'Bombay' and
  'para-Bombay' individuals (see 5.5.6) are generally accompanied by anti-A and anti-B, neither of which can be separated from the
  anti-H specific antibodies.
  
  
   Schenkel-Brunner, Helmut. Human blood groups: chemical and
  biochemical basis of antigen specificity. Springer Science &amp;
  Business Media, 2000. e-Book ISBN: 978-3-7091-6294-1