Cytokine indices in Alzheimer's temporal cortex: no changes in mature IL-1 beta or IL-1RA but increases in the associated acute phase proteins IL-6, alpha 2-macroglobulin and C-reactive protein

Abstract

Recent immunocytochemical data have demonstrated increases in interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and the IL-6-inducible acute phase protein, alpha 2-macroglobulin (alpha 2-M), in Alzheimer's disease (AD) brains. We investigated the levels of these proteins quantitatively using ELISA procedures and determined if increases in IL-1 beta were compensated for by a parallel increase in the endogenous interleukin-1 receptor antagonist (IL-1RA). Comparing control vs. Alzheimer's temporal cortex, we examined mature IL-1 beta, IL-1RA, IL-6, alpha 2-M and C-reactive protein (CRP). The specificities of the ELISA procedures were verified by serial dilutions of the samples; by chromatofocusing, and by Sephadex G-150 gel filtration. There were no differences in the levels of mature IL-1 beta or IL-1RA in AD and control brains. However, IL-6 levels were detectable in 14 of the 16 Alzheimer samples but only 2 of the 14 control samples. There were also significant increases seen in alpha 2-M and CRP levels in the Alzheimer's group compared to controls. These data support previous studies demonstrating a possible up-regulation of neuroimmune function in Alzheimer's cortex; however, we cannot determine, at this time, if this immune reaction is initiated by IL-1 beta.