CD40LG and malaria: While we have indirectly shown that IgM antibodies measured here are from memory B cells, our data are suggestive of IgM memory acquisition; in our cohort of PNG children, from an area of relatively high malaria transmission intensity, older children who have had greater overall malaria exposure had both higher merozoite-specific IgM and IgG levels compared to younger children, consistent with the acquisition of both memory antibody isotypes with increasing immunity.