A 19-year-old man presents with arthralgias and malar rash. Vital signs: BP 128/82, HR 92, RR 16, Temp 37.2°C, SpO2 98%. Labs reveal ANA 1:640 with anti-dsDNA antibodies; complement C3 level is low. He denies photosensitivity. Genetic testing shows a mutation preventing thymocyte apoptosis after high-affinity binding to self-peptide MHC complexes. Failure of which normal thymic process best explains his increased autoimmunity risk?
- A)Negative selection in the thymic medullaGABARITO
- B)Positive selection in the thymic cortex
- C)Class switching in activated B cells
- D)Affinity maturation in germinal centers
- E)Anergy in peripheral B cells
Explicação
Negative selection occurs in the thymic medulla, where thymocytes that bind strongly to self peptide MHC are deleted or diverted into regulatory T cells. Failure of this central tolerance mechanism allows autoreactive T cells to enter the periphery and increas... Ver explicação completa e trilha adaptativa →