<prompt> Brutons agammaglobulinemia is due to?B-cell defectIgA deficiencyIg M deficiencyIg G deficiency  <response>: X-Linked agammaglobulinemia of bruton There is defective humoral immunity with normal cell-mediated immunity. It is characterized by the failure of B cell precursors Pro-B cells and pre B cells to mature into B cells. There is a mutation in cytoplasmic tyrosine kinase called B - cell tyrosine kinase BtK.The disease usually does not become apparent until about age 6 months, when maternal immunoglobulins are depleted.B cells are absent or markedly decreased in the circulation and the serum levels of all classes of immunoglobulin. There are depletions of B cell area of lymph node Cortical follicles and medullary cord and spleen perifollicular region, germinal centre and mantle layer. Tonsil and adenoids are atrophicT-cell collection areas are normal i.e.i Paracortical area in lymph nodes, andii Periarterial lymphoid region malpighian corpuscle in white pulp of the spleen.The disease is seen almost entirely in males. There are recurrent bacterial infections of the respiratory tract by H. influenzae, str. pneumonia or staph aureus. There is increased susceptibility to infection with enterovirus echo, coxsackievirus, poliovirus, Giardia lamblia, and arthritis by mycoplasmaAs there is agammaglobulinemia, Opsonization is defective Immunoglobulins are the major opsonins in the body. 