“…On the basis of their behaviour and growth in vitro, their appearance in stained films and their fine structural organisation, the cells of the EB4 and EB5 strains are clearly of the same general lymphoblastic type as all the other cells established previously in culture from Burkitt tumours Pulvertaft, 1964;Stewart, Lovelace, Whang and Ngu, 1965;Epstein, Barr and Achong, 1965a;O'Conor and Rabson, 1965;Rabson, O'Conor, Baron, Whang, and Legallais, 1966;Osunkoya, 1966). In terms of detail, both the EB4 and EB5 cells are differentiated rather than undifferentiated lymphoblasts and therefore closer to EBI and EB3 cells (Epstein, Barr and Achong, 1965a) than to the undifferentiated EB2 (Epstein, Barr and Achong, 1965b), SL1 (Stewart, Lovelace, Whang and Ngu, 1965) or Raji cells (Pulvertaft, 1964;Epstein, Achong, Barr, Zajac, Henle and Henle, 1966); this is shown by their small size, regular rounded nuclei, relatively restricted cytoplasm and proliferation as single cells without forming regular clumps (Fig.…”