Immune reconstitution inflammatory syndrome (IRIS)- characterized by increased inflammatory response, subclinical oppounistic infections. common in patients with severe CD4 + T-lymphocyte depletion There is fever & worsening of clinical manifestations of oppounistic infection or new manifestations (e.g., enlargement of lymph nodes, pulmonary infiltrates), typically within the 1st few weeks after initiation of antiretroviral therapy.