CD40 and immune system disorder: Decreased expression of CD40 on monocytes of children with IgAD has previously been observed (Kowalczyk et al., 2006) and CD40 has also been implicated in the etiology of a variety of immune diseases such as RA, asthma, T1D and MS (Park et al., 2007; Australia and New Zealand, 2009; van der Linden et al., 2009).