In contrast to this finding, samples from patients with shorter disease duration or lower titers of specific IgM and IgG antibodies, such as sera from neuroborreliosis cases (62/2006 and 32/2008), past infections (serum scar: sample 21/2007), and cross-reacting samples such as sera from syphilis patients (61/2007), posed more significant diagnostic problems. The gene discussed is CD40LG; the disease is syphilis.