LACK OF CD39 DRIVES TERMINAL EXHAUSTION IN CD8+ T LYMPHOCYTES WITH A CYTOTOXIC PHENOTYPE.

CAROLINA ABRATE; VALENTINA BRUNOTTO; SABRINA BOSSIO; SANTIAGO BOCCARDO; ADRIANA GRUPPI; EVA ACOSTA RODRIGUEZ; CAROLINA MONTES

San Luis

Congreso; LXXI Reunión Anual de la Sociedad Argentina de Inmunología; 2023

SAI

CD39 is an ecto-enzyme that participates in the generation of adenosine(ADO),animmunosuppressive moleculethat interferes with many anti-tumorimmune responses.In this study, we assessed the influence of CD39 expression ontumor progression and its effect on CD8+ exhausted T Lymphocytes (LiT) within thetumor microenvironment. For this, C57BL/6 wild type (WT) and CD39 KO mice wereinjected subcutaneouslywithMC38tumor cells (0.5x106). By day 17 we evaluateddifferent tumor–infiltrating (T-I) immune cell populations. Additionally, weexaminedthe expression of inhibitor receptors (iRs) (PD-1, 2B4, Lag3 and TIM-3),transcription factors (TF) (Eomes.Tbet, IRF-4 and TOX) linked to exhaustion andcytotoxic related molecules, on T-ICD8+ T cells by flow cytometry. CD39KO miceexhibited a reduce tumor volume on days 12,14 and 17 days post tumor injection(p<0.05) than tumor-bearing WT mice. We observed no significant differences onT-I immune cell populations (B lymphocytes, CD4+ and CD8+ T cells, Treg, andMacrophages) among CD39KO and WT mice. WhileCD39KO mice showed similarfrequencies of T-I CD8+ T cells than WT mice, the former exhibited higher % of TI-LiTCD8+ co-expressing 4 IR (p<0.05), higher expression (measures as MFI) ofEomes, Tbet and IRF4 (p<0.05, p<0.0001), and higher% of Granzyme B (GrB) andPerforin expressing T-I CD8+ T cells (p<0.01). It has been reported thatintermediate expression of PD-1 (PD-1int) correspond to pre-exhausted LiT CD8+phenotype, while high PD-1 expression (PD-1high) denotes a terminal exhaustionphenotype. Thus, we detected that CD39 KO mice exhibited a higher % of TI-CD8+PD-1 high T cells than WT mice(p<0.05). In concordance, within the TI-CD8+PD-1 high T cells we found higher co-expression of IRs (p<0.05), higherexpression of TF associated to exhaustion and increased % of GrB and Perforincompared to TI- LiT CD8+PD-1 int.Furthermore, CD39KO mice demonstrated ahigher percentage of LiT CD8+PD-1 high expressing GrB and Perforin than WT mice(p<0.05, p<0.01). Together, the lack of CD39 leads to a decline in ATP metabolism,resulting in a reduction of ADO. Although the frequency of immune cells within tumormicroenvironment remains unaltered, the absence of CD39 fosters an increase ofterminally exhausted CD8+ T lymphocytes exhibiting a cytotoxic phenotype. This Tcell population may contribute to better control of tumor progression.