Immunostimulation by Silica Particles and the Development of Autoimmune Dysregulation

Another typical substance is silica. Patients exposed to silica particles were shown to develop not only pulmonary fibrosis, known as silicosis [9,10], one of the typical forms of pneumoconiosis, but also various autoimmune diseases

Suni Lee¹, Hiroaki Hayashi², Megumi Maeda³, Hidenori Matsuzaki¹, Naoko Kumagai-Takei¹, Ying Chen⁴, Kozo Urakami⁵, Masayasu Kusaka⁶, Yasumitsu Nishimura¹ and Takemi Otsuki¹

^[1] Department of Hygiene, Kawasaki Medical School, Kurashiki, Japan

^[2] Department of Dermatology, Kawasaki Medical School, Kurashiki, Japan

^[3] Department of Biofunctional Chemistry, Division of Bioscience, Okayama University Graduate School of Natural Science and Technology, Okayama, Japan

^[4] Division of Pneumoconiosis, School of Public Health, China Medical University, Shenyang, China

^[5] Hinase Urakami Iin, Bizen, Japan

^[6] Kusaka Hospital, Bizen, Japan

1. Introduction

Immunostimulation by environmental and occupational factors has been shown to cause various human diseases such as allergy and autoimmune diseases [1,2]. For example, solvents such as vinyl chloride have been linked to the development of scleroderma (SSc) [3-5], and previous studies reported the relationship between exposure to solvents and rheumatoid arthritis (RA) [6] or multiple sclerosis [7,8]. Another typical substance is silica. Patients exposed to silica particles were shown to develop not only pulmonary fibrosis, known as silicosis [9,10], one of the typical forms of pneumoconiosis, but also various autoimmune diseases [11,12] such as RA (historically known as Caplan syndrome) [13,14], SSc [15-17], systemic lupus erythematous (SLE) [18,19], and anti-neutrophil cytoplasmic antibody (ANCA)-related vasculitis/nephritis [20-22]. Many epidemiological reports have demonstrated that silica exposure is a risk factor of autoimmune diseases [11,12].

7. Conclusions

Even if core chemical substances, Si and O₂, are identical, the immunological effects of silica seem to be completely opposite to those of asbestos. Silica is a chronic stimulator of T cells, with chronic exposure leading to autoimmune dysregulation due to the chronic activation of responder T cells as well as Treg, resulting in an imbalance in the regulation of T cell responses. On the other hand, asbestos reduces anti-tumor immunity. Therefore, asbestos is not a stimulator, but can alter the function of immune cells.

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