The Capillary Walls

Immunohistochemical and ultrastructural observations on the capillary walls of AIDS brain cortex.

In a previous study on the immunohistochemical modification of capillary walls in AIDS brain cortex 1), an increase in laminin content was found in affected basement membranes. In this report, we have considered the expression of various types of collagen (I, III, IV and VI), as well as the ultrastructural appearance of the capillary walls. Immunoreactivity for type I and III collagens was found to be constantly negative. Type IV collagen was uniformly expressed in both control and AIDS brain tissue. Type VI collagen showed a variable pattern of reactivity. In control tissue, it was only occasionally expressed in the peripheral layer of larger vessels. In some of the AIDS cases (5 out of 7) an immunoreactivity was also present in the walls of smaller capillaries; in 3 cases, a distinct intracytoplasmic positivity was also detected in hypertrophic astrocytes. Ultrastructural observation showed focal thickening of basement membranes and occasional deposition of extracellular fibrillary matrix. Immunohistochemistry and electron microscopy can enlighten structural modifications of the capillary walls in neuroAIDS which may be easily missed at routine histological examination. 1)Taruscio et al. "Increased reactivity of laminin in the basement membranes of capillary walls in AIDS brain cortex", Acta Neuropathol, in press.