Intracellular inflammatory signalling cascades in human monocytic cells on challenge with phytohemagglutinin and 2,4,6-trinitrophenol.

Phytohemagglutinin (PHA) is a plant mitogen that can agglutinate human leukocytes and erythrocytes. PHA is mainly derived from red kidney beans and can act as an exogenous pyrogen. When entering into the blood circulation, exogenous pyrogens principally interact with monocytes and macrophages and induce the release of pro-inflammatory cytokines. Monocytes and macrophages are the cells that fight against foreign invaders and acts as a primary line of immune defence. Similar to PHA, the chemical 2,4,6-trinitrophenol (TNP) also acts as an exogenous pyrogen. The study focused on the in vitro interaction of PHA and TNP with the human monocyte/macrophage cell model THP-1. The exposure and associated change in cellular morphology, organelle function, mechanism of cell death, inflammatory signalling and expression of inflammation-related genes were analyzed in different time periods. It was observed that PHA and TNP induce dose and time-dependent toxicity to monocytes/macrophages where the mechanism of cell death was different for PHA and TNP. Both PHA and TNP can evoke immune signalling with increased expression of inflammatory genes and associated activation of intracellular signalling cascades.