Table II.

Tumor cells engineered to secrete GM-CSF suppress anamnestic CTL response

TumorTumor Size (mm)bGM-CSF in vitro (pg/ml)aGM-CSF in Vivo (pg/ml)bCD11b+ SplenocytesbAnti-β-Gal Response (LU30/106 Cells)c
No tumorNegativeND1.8213
B16 wt17 × 16003.0196
GM4217 × 1667184.512.2<10
GM3213 × 13719301.212.015
GM1517 × 14894800.717.4<10
GM1911 × 10868115.29.3<10
GM3717 × 13690158.513.1<10
GM3410 × 10877146.07.514
GM1218 × 1270211.78.310
GM4718 × 15626172.111.210
  • a Levels of GM-CSF released by 106 tumor cells after 18 h were evaluated on aliquots of the same cellular preparation injected s.c. to establish the tumor nodules.

  • b Major tumor diameters were measured in a blind fashion immediately before the mice were sacrificed to remove the spleens and set up the peptide-stimulated cultures. On the same day, blood samples were drawn from each mouse to determine the serum levels of GM-CSF (GM-CSF in vivo), and the spleens were analyzed for the presence of CD11b+ splenocytes.

  • c LU30 defined as the number of lymphocytes necessary to achieve 30% lysis of 2 × 103 β-gal peptide-pulsed target cells in a 4-h assay, were calculated from recovered viable cells.