<prompt> Answer this question truthfullyWhich immunoglobulin is most useful for diagnosing neonatal infections?  <response>: <reason> The most useful immunoglobulin for diagnosing neonatal infections is IgM. IgM antibodies are the first antibodies produced in response to an infection, and their presence in a newborns blood can indicate a recent infection. Other immunoglobulins, such as IgG, may also be present in a newborns blood, but IgM is the most useful for diagnosing neonatal infections. It is important to consult with a healthcare professional if you suspect that your newborn may have an infection. 