Unimpeded growth of tumour in hosts pre-immunized with tyrosyl- or dinitrophenyl-coated tumour cells.

Techniques are described for hapten attachment to the cell membranes of mouse tumour cells. Dinitrophenylation and tyrosylation could be achieved without substantial loss of viability as measured by dye exclusion. In addition hapten coated tumour cells were capable of initiating new tumour formation in syngeneic hosts. Pre-immunization of recipient mice with hapten coated tumour cells did not increase their resistance to tumour formation upon subsequent challenge with graded doses of untreated tumour cells.