[Potential role of the Nerve Growth Factor on Natural Killer Cells]. (Doctoral thesis)
- Allergy and Clinical Immunology
Nerve Growth Factor or NGF is a polypeptide composed of 3 subunits and it belongs to the neurotrophin family. As all the neurotrophines of this family, the NGF possesses two receptors: a specific one with high affinity called Tropomyosin Receptor Kinase A or TrkA and a low affinity one, the neurotrophin receptor or p75NTR common to all the neurotrophins. The fixation of the NGF to one of both receptors is sufficient for activating a signaling pathway. The NGF is known to play an essential role in the development, the survival and the maintenance of the peripheral and central nervous system. For several decades, numerous studies have shown that the NGF also plays an important role in the immune system. It has multiple effects on the immune cells because it can influence their proliferation, survival, apoptosis and degranulation. NGF can be produced by various immune cell types such as B lymphocytes, mastocytes, eosinophils, neutrophils, monocytes / macrophages or even T lymphocytes. Sacerdote and collaborators, indirectly showed the presence of TrkA and / or p75NTR on splenic NK cells from rats (Sacerdote et al, 1996). Human NK cells from peripheral blood express TrkA (Nassenstein et al, 2006 ; Rogers ML et al, 2010). The experiments made by Rogers and co-workers show that in the presence of IL-2 alone, TrkA is expressed but not p75NTR. Importantly, on NK cells cultured with IL-12, p75NTR expression is augmented and the proNGF increases the apoptosis of NK cells.
In front of the little data available on the effect of the NGF on cells NK, we began to study its role on cells NK from mouse C57BL/6 mice. Our work demonstrates the presence of TrkA on NK cells from the spleen, lungs, blood, and bone marrow whereas p75NTR is only discovered at a low percentage. On the splenic NK cells, TrkA is upregulated and is expressed by about 100 % of cells put in culture with IL-2 during 5 days whereas in the same conditions, p75NTR expression doesn't change. The use of the confocal microscopy confirms the presence of TrkA on the activated NK cells. With this technique, p75NTR is not detected on fresh and IL2-stimulated NK cells. Then, we were interested in the expression of TrkA on cells NK according to their degree of maturation. NK cells can be subdivided into 4 sub-populations according to the expression of CD27 and CD11b, CD11b+ NK cells being the most mature. We observed two profiles of TrkA expression : at day = 0, a bigger proportion of CD27+ NK cells express TrkA compared to CD27- NK cells ; furthermore, in culture with IL-2, TrkA appears more quickly on CD27+ NK cells than on CD27- NK cells. The use of several concentrations of NGF on NK cells cultured during 3 days with IL-2 shows that the NGF has no effect on the survival, the apoptosis, the proliferation, the expression of cell surface markers, or on the secretion of IFNg. Nevertheless, the degranulation of NK cells incubated during 5h with IL2+IL12+IL18+NGF is decreased when NK cells are pre-cultured with IL-2+NGF compared to cells pre-cultured with IL-2 during 3 days. The NGF thus partially inhibits NK cell degranulation. Finally, given that the NGF is known to increase the allergic reaction, we were interested in the effect of the NGF on NK cells from mice after immunizations and nasal instillations of ovalbumin.