ICAR AIEEA PG 2024 - Veterinary Science

Anthracosis is an environmental pneumoconiosis characterized by the asymptomatic inhalation and deposition of exogenous carbon or coal dust particles in pulmonary alveolar macrophages and peribronchial lymph nodes. Siderosis is iron dust deposition, silicosis is silica inhalation, and plumbism is chronic lead poisoning.

The physiologic pathogenesis of pyrexia proceeds in order:

• Exogenous pyrogens (microbial toxins/infections) enter the bloodstream (A)
• Phagocytic leukocytes produce and release endogenous pyrogenic cytokines (IL-1, IL-6, TNF-alpha, IFNs) (C)
• Cytokines stimulate the vascular endothelium of the organum vasculosum laminae terminalis (OVLT) in the hypothalamus to synthesize Prostaglandin $E_2$ ($PGE_2$) (D)
• $PGE_2$ elevates the hypothalamic thermoregulatory set-point, triggering peripheral cutaneous vasoconstriction to conserve heat, resulting in fever (B).

Both Statement (I) and Statement (II) are true: circulating IgE levels are the lowest among all serum immunoglobulins because monomeric IgE has an exceptionally high affinity ($K_a \approx 10^{10} \text{ M}^{-1}$) for $Fc\varepsilon RI$ receptors on tissue mast cells and basophils, leaving almost all IgE cytophilic and cell-bound. Unlike IgG or IgM, IgE cannot simply neutralize or opsonize soluble antigens in fluid phase; it functions by cross-linking cell-bound $Fc\varepsilon RI$, which triggers mast cell degranulation and release of vasoactive mediators.