ICOS and infection: In conclusion, present study reveals that high levels of CD4+ICOS+Foxp3+ cells and IL-10 during the course of infection with P. berghei and P. yoelii 17XL suppresses immune system of host that might help parasite to grow faster, however there is no significant expression of these highly immunosuppressive cells in P. chabaudi and P. yoelii 17XNL infection.