Nezelof's Syndrome is an extremely rare immune
deficiency disorder characterized by the impairment of cellular immunity against infections, especially by those agents that
do not normally cause serious illness (opportunistic infections). In cell-mediated immune responses, specialized white blood
cells known as T lymphocytes or "killer cells" help B lymphocytes respond to infectious foreign agents that invade the body.
Nezelof's Syndrome may also include some abnormalities in humoral immunity. In this form of immune response, antibodies that
are produced by specialized cells (i.e., B lymphocytes) circulate in the lymphatic fluid and blood. Antibodies fight off bacteria,
viruses, and other foreign substances that threaten the body. B lymphocytes enable the body to produce and maintain circulating
antibodies. In a subgroup of people with Nezelof's Syndrome, immune deficiency may be caused by a lack of the enzyme purine
nucleoside phosphorylase (PNP).
Credit to - www.rarediseases.org