Four serotype 1 field strains of infectious bursal disease virus (IBDV
) and one reference standard serotype 1 strain were tested for their a
bility to agglutinate peripheral blood lymphocytes of chickens. All th
e five strains agglutinated chicken lymphocytes. The agglutination was
not inhibited by serotype 1 reference anti-IBDV serum. These results
suggest the need for detailed analysis of lBDV ligand(s) and cell surf
ace receptor(s) relationships.