PF4 and malaria: The fact that PF4-123 and PF4-143 had no significant difference in total antibody IgG levels between sick and healthy participants and the significantly higher level of cytophilic antibodies (IgG1 and IgG3) in healthy participants, suggest that antibodies to these antigens are constitutively produced and may be necessary for the reduction of risk of contracting malaria in this geographical region.