In vitro production of a cell population using feeder cells

A method for the in vitro expansion of a mammal Tr1 cell population P′, from a purified or enriched mammal Tr1 regulatory cell population P, in a culture medium Mp, said expansion requiring the presence of at least five factors in said culture medium Mp, said method comprising:

• (a) cultivating insect feeder cells at a temperature T1 and in a culture medium Mf, said insect feeder cells capable of expressing said at least five factors, the T1 being a temperature that allows proliferation of said feeder cells, and said at least five factors comprise:
• (i) an anti-CD3 monoclonal antibody anchored to the insect feeder cell membrane, and
• (ii) a CD80 protein, a CD86 protein or an anti-CD28 monoclonal antibody, said CD80 protein, CD86 protein or anti-CD28 monoclonal antibody being anchored to the insect feeder cell membrane and capable of cross-linking a CD28 molecule;
• (iii) a CD58 protein anchored to the cell membrane of the insect feeder cells, the CD58 protein being capable of interacting with the CD2 protein of the Tr1 cells,
• (iv) an IL-2 secreted by the insect feeder cells, the IL-2 being capable of interacting with the IL-2 receptor of the Tr1 cells, and
• (v) an interleukin selected from the group consisting of IL-4 and IL-13, said interleukin being secreted by the insect feeder cells and capable of interacting with the IL-4 receptor of the Tr1 cells;
• (b) contacting the insect feeder cells obtained at step (a) with the Tr1 cell population P in the culture medium Mp, wherein said culture medium Mp does not initially contain the at least five factors, to obtain a mixture containing the Tr1 cell population P, the insect feeder cells and the culture medium Mp,
• c) cultivating the mixture obtained at step (b), wherein the at least five factors are expressed by the insect feeder cells in the culture medium Mp, and said cultivating is carried out at a temperature T2, said temperature T2 being chosen such that:
• the Tr1 cell population P proliferates, and
• the insect feeder cells do not proliferate, thus expanding the Tr1 cell population P′;
• and
• d) recovering the Tr1 cell population P′ so expanded,
• wherein said method is capable of maintaining exponential growth of the Tr1 cell population P′ for at least one month.