Fig. 4: Collagen induces CD8⁺ T cell exhaustion through LAIR1-mediated SHP-1 signaling.

a Proposed model illustrating LAIR1 binding to collagen, which induces SHP-1-mediated T cell exhaustion alternative to the PD-1 pathway. LAIR1 signaling can be inhibited by secreted LAIR2 homolog binding to the LAIR1 collagen epitope or small-molecule inhibition of SHP-1. b Schematic of in vitro co-culture experiments. Splenocytes isolated from WT mice were co-cultured on collagen versus on plastic as a control in LAIR2-conditioned media, media containing SHP-1 inhibitor (TPI-1) or SHP-2 inhibitor (SHP099), and then analyzed by FACS. c FACS percentage of total CD8⁺ (left), PD-1⁺TIM-3⁺ CD8⁺ (middle), and LAIR1⁺ CD8⁺ (bottom) T cells in splenocytes co-cultured on plastic or collagen treated with 10µM SHP-1 inhibitor (TPI-1), 20 µM SHP-2 inhibitor (SHP099), or DMSO control for 96 h; n = 3 technical triplicates. d FACS percentage of total CD8⁺ (left), PD-1⁺TIM-3⁺ CD8⁺ (middle), and LAIR1⁺ CD8⁺ (right) T cells in splenocytes co-cultured on plastic or collagen for 96 h in conditioned media from 344SQ cells expressing LAIR2 or vector control; n = 3 technical triplicates. e FACS percentage of LAIR1⁺ CD8⁺ T cells for indicated 344SQ tumor cell suspensions from the experiment in Supplementary Fig. 5; n = 4 tumors per group. f FACS percentage of LAIR1⁺ CD8⁺ T cells for indicated 344SQ tumor cell suspensions from the experiment in Fig. 3; n = 5 tumors per group. g Heatmap showing association of mRNA expression in TCGA LUSC dataset between LAIR1 and collagen receptor genes that are statistically significant (P < 0.05) by Spearman’s rank correlation. h Representative scatter plot analysis of Spearman’s rank correlation between ITGB2, ITGAL, ITGAM, and ITGAX versus LAIR1 mRNA expression in TCGA LUSC dataset. i–k Splenocytes cultured in vitro on plastic, laminin-rich Matrigel, or collagen were treated with CD18 inhibitory antibody (10 µg/mL) for 96 h and analyzed by FACS for percentage of (i) total CD8⁺ T cells gated from CD45⁺CD3⁺ splenocytes, (j) LAIR1⁺ CD8⁺ T cells, and (k) PD-1⁺TIM-3⁺ exhausted CD8⁺ T cells; n = 3 technical replicates per group. Unless stated, all data presented as mean +/− SD and statistics calculated using a one-way ANOVA post hoc Tukey test.