Sequential immunological studies on an asbestos-exposed population. I. Factors affecting peripheral blood leucocytes and T lymphocytes.

Peripheral blood leucocyte counts, and E binding rosettes were measured on 138 men on five separate occasions. Little effect was seen from age, or length of asbestos exposure. Overall the most marked effect was that obtained from smoking. Most relevant was an increase in percentage of E-rosettes read after 1 1/2 hrs, which was obtained in the group of those with radiological evidence of fibrosis who smoked. Restricted to subjects with small opacities, those who smoke have a significantly higher (P less than 0.05) percentage E 1 1/2 hr rosettes than those who do not smoke. (Percentage E rosettes read overnight remained unaltered by smoking or X-ray). This increase was found on each occasion that it was measured. Since the absolute number of T lymphocytes rosetting at 1 1/2 hr did not increase, it is suggested that there is either no stimulation of the central pool of T lymphocytes or a decrease in the absolute number of T lymphocytes which could only rosette overnight.