KINETICS OF TONSILLAR LYMPHOID PROLIFERATIVE RESPONSES EX VIVO

ROCÍO A. PASTOR; JULIANA PUYSSEGUR; LINDYBETH SARMIENTO VARÓN; GONZALO HUSAIN; M. ELENA ARABOLAZA; BIBIANA P. PAOLI; ELOÍSA I. ARANA

Mar del Plata

Congreso; Congreso Anual Soc Argentina de Inmunologia; 2022

The mucosa of the oronasopharynx is the gateway for the majority of pathogens. Efforts in vaccine development aimed at local mucosal immune responses would yield benefits particularly relevant in the current pandemic context. Although is known to be induced partly via the tonsils and adenoids, the responses at this site are poorly understood. Our aim was to characterize the proliferative response for the different tonsillar lymphocyte population ex vivo. Cell prolif- eration was monitored after tonsillar mononuclear cells (TMC) were stimulated with either IL2/IL4 or IL2/IL4/CpG/CD40L in the culture, by scoring Ki-67+ cells using FACS. We analyze 3 lymphoid popula- tions (CD20+, CD3+CD4+ and CD3+CD8+) at 3 different time points (24, 48 and 72 hours) for 5 patients. We found that B and T cells steadily expanded from 24 hs up to 72 hs in IL2/IL4/CpG/CD40L cultures. Completed 72hs of culture, around one third of tonsillar B cells expressed Ki-67 (30% ± 13,7%). Maximum levels reached by CD4+ and CD8+ T cells were 11,4%± 4,1% and 11,7%± 4,2% Ki- 67+ cells, respectively. On the other hand, T cells showed a better response than B cells in IL2/IL4 cultures. At the last time point, while the CD3+CD4+Ki-67+ cells represented 8,9%± 7,2% of the CD4+ T cells and CD3+CD8+Ki-67+ were 8,6%± 1,8% of the CD8+ T cells, proliferating B cells accounted for only 3,8% ± 1,2% of total CD20+ cells. Finally, we investigated the expression of CD73, known to pro- mote stemness and exhaustion in peripheral T cell populations, on stimulated tonsillar B and T cells. CD73 appeared downregulated in all stimulated lymphocytes. The ability for vigorous proliferation upon re-infection is a trait of adaptive immunity and the basis of vaccination. CpG is a Toll like receptor ligand, experimentally used as a vaccine adjuvant. We propose our system of culture to rapidly test mucosal vaccine and adjuvants candidates. Of note, mucosal vaccine responses in mice are often poorly predictive of results in humans