HAVCR2 and Pleuritis: In MPM, one study found TIM-3 and TIGIT protein upregulated on CD8+ cells when compared with tumor-free lung-associated CTLs, while approximately 60% were PD-1 positive.20 PD-1, LAG-3 and TIM-3 protein on CTLs were found to be elevated in MPM samples versus pleuritis,30 suggesting that exhaustion may be widespread and a consequence of multiple, redundant interactions in this disease.