Deep Phenomics of Pattern Recognition Receptor Agonist Specific Activation of Human Blood

Human whole blood (WB) immunophenotyping may represent the in vivo immunological state with better fidelity than artificially isolated peripheral blood mononuclear cells (PBMCs). We used a deep phenomics modeling approach to elucidate the quantitative differences in major immune cell lineages in WB and PBMC compartments in a steady-state in vitro setting. We studied functional innate immune responses induced by pattern recognition receptor agonist adjuvants (PRRa). Using an optimized 49-parameter CyTOF panel and implementing machine learning (ML) algorithms, we mapped PRRa-mediated CD69, CD40, CD80, CD86 and CCR7 activation at the nodal innate immune subsets level. We also portrayed cellular origin of innate functional chemokine CCL4 and intracellular cytokine IFNγ production. We mapped neutrophils as the primary source of TLR7/8 agonist (TLR7/8a) and STING agonist mediated CCL4 responses in WB. Notably, in the PBMC fraction, where neutrophils are limited, natural killer (NK) cells became the major source of innate CCL4 production. TLR7/8a-mediated IFNγ induction by early NK cells was mapped in PBMCs, which was limited in WB. Considering such distinctions, we hypothesized that deep phenomics employing a clinical sample that has not been manipulated, i.e., WB, may be additive in translating in vitro innate fingerprinting into in vivo biology.