]> 2026-07-31T11:51:17+00:00 WBR0691 0 en Type I hypersensitivity Type I hypersensitivity involves IgE-mediated reaction in which an antigen crosslinks two IgE antibody molecules on pre-sensitized mast cells. Subsequently, mast cells release histamines, leukotrienes, and prostaglandins. Anaphylaxis is an example of type I hypersensitivity. Type II hypersensitivity Type II hypersensitivity reactions are either IgM- or IgG-mediated, where antibodies attach to antigens on cell surfaces followed by complement-mediated lysis of cells. In Goodpasture’s syndrome, antibodies against antigen present in type IV collagen target GBM and alveolar basement membrane, both of which are rich in type IV collagen. Type III hypersensitivity Type III hypersensitivity involves antigen-antibody immune complexes. In this reaction, the antigen is not attached to tissues. Immune complexes circulate in blood and are deposited in various tissues where they activate complement and induce an inflammatory reaction. Type IV hypersensitivity Type IV hypersensitivity (delayed type hypersensitivity) is a cell-mediated response unlike other antibody-mediated hypersensitivity reactions. CD-4 helper T cells recognize antigens presented by antigen-presenting cells (APC) on major histocompatibility complex type II. Activated helper T cells release lymphokines and interferon gamma, which lead to the activation of macrophages. Mixed hypersensitivity Goodpasture's syndrome is a type II hypersensitivity. it is not a mixed hypersensitivity. An example of mixed hypersensitivity is hypersensitivity pneumonitis (type III and type IV). Immunology A 20-year-old man presents with complaints of chronic dry cough that has recently become associated with bloody sputum. His cough is associated with intermittent low-grade fever, malaise, shortness of breath, chest pain, and bloody urine. Chest X ray demonstrates bilateral patchy areas of consolidation. Urine examination is remarkable for the presence of red blood cell casts and protein. Serologic assays are positive for anti-GBM antibodies and negative for ANCAs. Which of the following types of hypersensitivity reactions is responsible for this patient’s condition? B Pulmonology Renal 2020-10-28T01:25:46Z 2459150.5595602 WBR0691