Release of LL-37 by activated human Vγ9Vδ2 T cells:: A microbicidal weapon against Brucella suis

Human V gamma 9V delta 2 T cells play a crucial role in early immune response to intracellular pathogens. Moreover, in brucellosis, these cells are drastically increased in the peripheral blood of patients during the acute phase of infection. In vitro, V gamma 9V delta 2 T cells are capable of inhibiting Brucella growth and development through a combination of mechanisms: 1) cytotoxicity, 2) macrophage activation and bactericidal activity through cytokine and chemokine secretion, and 3) antibacterial effects. We previously described that antibacterial factors were found in supernatants from activated V gamma 9V delta 2 T cells. In this study, we show that V gamma 9V delta 2 T cells express the human cathelicidin hCAP18 and its mature form, known as LL-37, is released upon activation of V gamma 9V delta 2 T cells. We also show that LL-37 has an antibacterial effect on Brucella suis. Overall, our results demonstrate that LL-37 is a soluble factor responsible for a part of the bactericidal activity of V gamma 9V delta 2 T cells.