Polymorphisms in lymphotoxin alpha and CD14 genes influence TNFα production induced by Gram-positive and Gram-negative bacteria

Improved understanding of how host genetic variation affects resistance to microbial pathogens could lead to better treatment and/or prevention of infectious diseases. The lymphotoxin alpha (LTA)+250 and CD14-159 polymorphisms are associated with differences in susceptibility or outcome to several infections. We stimulated peripheral blood mononuclear cells (PBMC) from 22 healthy individuals with purified lipopolysaccharide (LPS), heat-killed Escherichia coli or Streptococcus pneumoniae. TNFalpha intracellular protein levels were measured by flow cytometry and mRNA was quantitated by RT-PCR. TNFalpha mRNA levels were higher in LTA+250GG subjects after 4 h incubation with LPS compared with LTA+250AA (T test, P = 0.001). In contrast, after 8 h incubation with S. pneumoniae, there was slightly more TNFalpha mRNA in cells from LTA+250AA subjects. After 4 h incubation with LPS or E. coli, CD14-159TT subjects had higher TNFalpha mRNA levels than CD14-159CC (P = 0.05, 0.033, respectively). Neither polymorphism affected the proportion of cells expressing intracellular TNFalpha protein. This suggests that the polymorphisms affected transcription and that other regulatory mechanisms affect production of TNFalpha protein. The effect of these two polymorphisms on TNFalpha mRNA production is stimulus dependent, with opposite effects observed for Gram-positive and Gram-negative stimuli.