Rheumatic Aschoff nodules revisited. II: Cytokine expression corroborates recently proposed sequential stages

A recent immunohistochemical analysis of the Aschoff lesions in rheumatic fever, combining immunohistochemical analysis with comparative morphology, permitted the division of the Aschoff nodules into three stages: (1) Aschoff nodule without admixed lymphocytes, (2) Aschoff nodules with a few T lymphocytes, and (3) Aschoff nodules containing many admixed lymphocytes of both B- and T-cell phenotype. It was postulated that the order of progression was from stage 1 with macrophages only, to accumulation of first T lymphocytes (stage 2) and then B lymphocytes (stage 3). This study was undertaken to determine the role and distribution of interleukin 1 (IL-1), interleukin 2 (IL-2) and tumour necrosis factor alpha (TNF alpha) in the various stages of the rheumatic Aschoff nodule to investigate our hypothesis on the progression of these nodules.

Sixteen fresh valve specimens from patients with acute rheumatic fever undergoing valve surgery were obtained. Tissue sections from 14 specimens identified as containing Aschoff nodules were subjected to immunohistochemistry for (1) T and B lymphocytes, to stage the lesions according to our previously proposed criteria; (2) IL-1, IL-2 and TNF alpha; and (3) CD4 and CD8 to phenotype the T lymphocytes. The stage 1 and 2 lesions expressed IL-1 and TNF alpha in the macrophages. The stage 3 lesions showed more variable expression of all three cytokines including IL-2 within T lymphocytes.

TNF alpha and IL-1 secretion in macrophages is required for T and B lymphocytes activation and aggregation; suggesting that macrophages arrive at the scene of rheumatic injury prior to the lymphocytes. IL-2 is usually expressed later in the inflammatory process and was found only in the lymphoid aggregates. This study therefore produces corroborative evidence for our previously proposed developmental stages of the Aschoff nodule.