T-lymphocyte activation in the enlarged thoracic lymph nodes of rats with silicosis.
Silicosis is primarily a mononuclear cell inflammatory and fibrotic disease of the pulmonary parenchyma. It is known that lung-associated lymph nodes are also affected. To study the involvement of lymphocytes in silicosis, we examined lymph nodes of rats 12 months after an 8-day silica aerosol exposure. We found that 2 thoracic lymph nodes close to the thymus were enormously enlarged in silicotic rats and contained a 49-fold higher cell number than control lymph nodes. The higher cell number was caused by parallel increases in T- and B-lymphocytes, natural killer (NK) cells, and macrophages without change in the relative proportions when compared with control thoracic lymph nodes. By examining interleukin-2 (IL-2) receptor and intercellular adhesion molecule-1 expression, we detected a significantly higher percentage of activated CD8+ T cells and, to a lower degree, of CD4+ T cells in thoracic lymph nodes of silicotic animals. In contrast, no differences in the activation state were found in T cells obtained from cervical or mesenteric lymph nodes of silicotic and control rats. The occurrence of activated T cells in thoracic lymph nodes of silicotic rats was documented further by selectively enhanced interferon-gamma (IFN-gamma) mRNA expression in the absence of IL-2 and IL-4 mRNA changes. These data show that T-lymphocytes of thoracic lymph nodes have become activated with an enhanced IFN-gamma gene transcription which may be an important cause of macrophage activation during silicosis.
Garn
H
H
Institute of Immunology, Philipps University of Marburg, Germany.
Friedetzky
A
A
Davis
G S
GS
Hemenway
D R
DR
Gemsa
D
D
D000818:Animals; D016207:Cytokines / Q000235:genetics; D015870:Gene Expression; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis; D007962:Leukocytes; D008198:Lymph Nodes / Q000276:immunology* / Q000473:pathology; D008213:Lymphocyte Activation / Q000276:immunology*; D016131:Lymphocyte Subsets; D008264:Macrophages; D008297:Male; D009929:Organ Size; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344; D015375:Receptors, Interleukin-2 / Q000032:analysis; D012829:Silicosis / Q000276:immunology*; D013601:T-Lymphocytes / Q000737:chemistry / Q000276:immunology*; D013909:Thorax
D016207:Cytokines; D012333:RNA, Messenger; D015375:Receptors, Interleukin-2; D018799:Intercellular Adhesion Molecule-1