Which of the following immunoglobulin is absent in Ataxia telangiectasia:

Ataxia telangiectasia (AT) Present in the first decade of life with progressive telangiectatic lesions associated with deficits in cerebellar function and nystagmus. There is a high incidence of recurrent pulmonary infections (bronchiectasisQ) and neoplasms of the lymphatic and reticuloendothelial system. It is caused due to defect in DNA repair genes Thymic hypoplasia with cellular and humoral (IgAQ and IgG2) immunodeficiencies, premature aging and endocrine disorders such as insulin resistance or type-I DM The most striking neuropathologic changes include loss of Purkinje, granule and basket cells in the cerebellar coex as well as of neurons in the deep cerebellar nuclei. A poorly developed or absent thymus gland is the most consistent defect of the lymphoid system.