Table 2

Inhibition of NK activity by the addition of platelets

The inhibitory capacity of platelets from mice of different strains and the influence of aggregation inhibitors hirudin (1 unit/ml), heparin (1 unit/ml), apyrase (5 units/ml), anti-P-selectin MAb (10 μg/ml), 2-h platelet supernatant, or 2-h platelet + YAC1 supernatant were determined in a 4-h 51Cr-release NK assay using C3H/HeN spleen cells as source of NK cells. The data given were obtained with an E:T ratio of 100:1 and in the presence of 10,000 platelets per YAC1 tumor cell. Specific lysis without the addition of platelets or inhibitors was 36.6 ± 1.2% in A, 46.5 ± 1.1% in B, and 11.6 ± 0.4 in C.
Platelet donor mouse strainAdded substanceInhibition of specific lysis %
A
 −0
 C3H/HeN54.7 ± 4.5
 C57BI/656.1 ± 1.1
 C57BI/6/SVJ12953.8 ± 2.5
 NMRI64.2 ± 0.8
 β2-Microglobulin−/−46.6 ± 2.4
B
 C3H/HeNHirudin0.5 ± 4.4
 C3H/HeNHeparin41.3 ± 3.2
 C3H/HeNApyrase38.1 ± 4.3
 C3H/HeNAnti-P-selectin36.0 ± 4.5
 C3H/HeNRat IgG65.8 ± 7.0
C
 −0
 C3H/HeN77.4 ± 4.6
 −Platelet supernatant32.8 ± 5.2
 −Platelet + YAC1 Supernatant30.4 ± 4.8