Immunocompromised states Flashcards
What do post-splenectomy pts lack that increases risk of infection?
Normally, blood borne antigens enter the spleen via the splenic artery and are phagocytes by dendritic cells in the white pulp. These dendritic cells then present antigens in association with MHC II to TH cells, activating them. Activated TH cells then migrate to the marginal zone of the spleen where they come into contact with B cells in primary follicles. B cell activation causes secondary follicles and plasma cell rich germinal centers to form. Antibodies produced in germinal center plasma cells enter the systemic circulation, bind their specific Ag, and facilitate phagocytosis of pathogenic organisms by opsonization. Splenic pts are less able to mount this sort of Ag-specific Ab response and are therefore at high risk of overwhelming infection by encapsulated organisms like S. pneuma, N. meningitides, and H. influenza
What should you suspect in pt wit palpable purpura, proteinuria and hematuria?
Mixed cryoglobulinemia. Pts have other clinical mx like nonspecific systemic sx, hepatosplenomegaly and hypocomplementemia. Majority of patients have underlying HCV infection.
Why do patients with pernicious anemia get vitamin B12 deficiency?
PA is duet o the presence of autoantibodies against gastric intrinsic factor, which is redquired for B12 absorption. PA is the most common cause of Vitamin B12 deficiency in whites of northern European background.
