<prompt> Buons agammaglobulinemia is due to?B-cell defectIgA deficiencyIg M deficiencyIg G deficiency313  <response>: Ans is a i.e. B-cell defect X-Linked agammaglobulinemia of buonThere 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 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 is depletions of B cell area of lymphnode Coical follicles and medullary cord and spleen perifollicular region, germinal centre and mantle layer. Tonsil and adenoids are atrophic.T-cell collection areas are normal i.e. i Paracoical area in lymph nodes, and ii Periaerial lymphoid region malpighian corpuscle in white pulp of spleen.The disease is seen almost entirely in males. There is recurrent bacterial infections of respiratory tract by H. influenzae, str. pneumoniae or staph. aureus. There is increased susceptibity to infection with enterovirus echo, coxsackievirus, poliovirus, giardia lamblia, and ahritis by mycoplasma.As there is agammaglobulinemia, Opsonization is defective Immunoglobulins are the major opsonins in body. 