PLASMABLAST WITH HIGH EXPRESSION OF CD39 AND PD-L1 INFILTRATE TUMORS FROM B16F10-OVA TUMOR-BEARING MICE

Mar del Plata

Congreso; LXX REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA (SAI) & 3ER CONGRESO FRANCO-ARGENTINO DE INMUNOLOGÍA (FAIC); 2022

Sociedad Argentina de Inmunología

The role of B cells in the anti-tumor response is not completely elucidated.B cells may play a dual role promoting or inhibiting cancerprogression depending on their phenotype and the microenvironment.In this work, we aim to study the phenotype of tumor- infiltrating(TI) B lymphocytes (LiB) in a murine melanoma model. NonSPF C57BL/6 mice were injected intraperitoneally (ip) with 4x105B16F10-OVA tumor cells or PBS (controls). On day 13, tumors andperitoneal lavage (PL) were collected and by flow cytometry, westudied different LiB subsets such as: B2, B1a, B1b. The frequencyof LiB (CD19+B220+) in PL from tumor-bearing mice was significantlylower respect to PL from control mice (p≤0.0001). Most of these Bcells correspond to B2 subset; in fact, B1a and B1b were nearlyabsent. Surprisingly, B1a and B1b subsets were almost missing inthe tumor microenvironment. Within the TI-LiB we observed that a61,55 ± 6,48% correspond to B cells exhibiting an unswitched phenotype,18,53 ± 2,82 % an activated phenotype and 18,08 ± 4,03%exhibited plasmablast/plasma cells phenotype (CD138+). Most ofthe of the CD19+B220+CD138+ cells expressed IgM (49,86 ± 7,85%)and 17,88 ± 1,60 % expressed Ki67. We also evaluated the expressionof PD-L1 and CD39 molecules involved in the regulation of theimmune response. CD39 is an ecto-enzyme, which participate inadenosine production, a potent immune-regulator. Almost 90% ofthe CD19+B220+CD138+ cells showed high expression of CD39 andPD-L1. Additionally they expressed activation markers such as MHCclass II and Fas. Interestingly, TI- activated B cells show a lowerexpression of PD-L1 and CD39 and TI- unswitched B cells do notexpress neither CD39 nor PD-L1. Together, these results show thatTI-CD138+ cells express modulatory molecules that may be involvedin the regulation of the immune response against tumors.