Comparison of the microanatomical distributions of macrophages and dendritic cells in normal and diseased tonsils

The palatine tonsils play an important role in immunologic surveillance and resistance to infection in the upper aerodigestive tract. Dendritic cells and macrophages function to capture and process antigen and present it to T lymphocytes, a critical step in the early immune response. Few studies have characterized the distribution and phenotype of those antigen-presenting cells in the normal palatine tonsil, or determined how those parameters change with disease. Immunohistochemical analysis was performed to determine the microanatomical distribution, quantity, morphology, and phenotype of macrophages and dendritic cells in both normal and diseased tonsils. Differences were observed in macrophage and dendritic cell distribution, quantity, and phenotype in the surface and crypt epithelium. The number of macrophages was significantly increased in all compartments in all disease groups (p < .05), although the number of macrophages that expressed phenotypes of maturity and/or activation was not concomitantly increased. In the surface epithelium, Langerhans and interdigitating cells decreased significantly with disease (p < .05). Chronic infection may impose an immunosuppressive effect on responses within tonsil tissue, affecting the immunologic factors responsible for macrophage maturation and activation.

Quantitative study of germinal center area in normal and diseased tonsils using image analysis

The aim of this study was to measure the germinal center area of secondary follicles in a consistent and unbiased manner using image analysis. Tonsil specimens were obtained from children with clinical evidence of recurrent tonsillitis and/or idiopathic tonsillar hypertrophy. Normal control biopsy specimens were obtained from children with no history of ear, nose, or throat infections. The results show a significant increase in the germinal center area in tonsils exhibiting hypertrophy when compared to normal controls (p < .002). Image analysis is an important tool for making quantitative size comparisons in lymphoid tissues.

Neuronal-associated tumor necrosis factor (TNF alpha): its role in noradrenergic functioning and modification of its expression following antidepressant drug administration

Tumor necrosis factor-alpha (TNF alpha) and the alpha 2-adrenergic agonist clonidine regulate norepinephrine (NE) release from noradrenergic nerve terminals in the central nervous system (CNS). In the present study, superfusion and electrical field stimulation were applied to a series of rat hippocampal brain slices in order to investigate the regulation of [3H]-NE release. NE release had been previously determined to be decreased by TNF alpha in a concentration-dependent manner, an effect which was potentiated by the alpha 2-adrenergic antagonist idazoxan. Presently, we demonstrate that similar to alpha 2-adrenergic activation, TNF alpha regulation of NE release in a region of the brain rich in noradrenergic nerve terminals, is dependent upon the frequency of electrical stimulation applied to the hippocampal slice. Furthermore, immunoperoxidase staining has verified our previous findings of constitutive TNF alpha protein in the rat brain. Staining for TNF alpha appears to be largely localized to neurons and neuronal processes, further substantiating the proposal that TNF alpha is either synthesized de novo or is accumulated in and released by neurons. After administration of the tricyclic antidepressant desipramine, tissue sections obtained from the rat hippocampus and locus coeruleus are devoid of neuronal-associated TNF alpha immunoreactivity. TNF alpha localization in neurons and its modification of NE release comparable to alpha 2-adrenergic receptor activation, explains a functional role for the cytokine as a neuromodulator in the CNS.