tet·ra·va·lent 
(tĕt′rə-vālənt)
(tĕt′rə-vālənt)adj.
1. Chemistry Having valence 4.
2. Immunology
a. Having four sites of attachment. Used of an antibody or antigen.
b. Containing antigens from four strains of a microorganism or virus. Used of a vaccine or serum.