CD40LG and susceptibility to pneumonia measurement: However, despite recurrent culture-proven pneumococcal infections such as pneumonia IgG-Pn23-antibodies were low (representing a mix of IVIG-derived and patient-derived antibodies), while IgM-Pn23-antibodies (entirely derived from the patient) were very high, resulting in a ratio of IgG- to IgM-Pn23-antibody serum titer that was well below the minimal value observed in our laboratory in healthy adults either before or after Pn23 vaccination.