Organized lymphatic tissue (BALT) in lungs of rhesus monkeys after air pollutant exposure

Abstract

The presence of bronchus-associated lymphoid tissue (BALT) and its size in humans largely depends upon age. It is detected in 35% of children less than 2 years of age, but absent in the healthy adult lung. Environmental gases or allergens may have an effect on the number of BALT. Lungs of rhesus macaque monkeys were screened by histology for the presence, size, and location of BALT after exposure to filtered air for 2, 6, 12, or 36 months or 12 and 36 months to ozone or 2, 12, or 36 months of house dust mite or a combination of ozone and house dust mite for 12 months. In the lungs of monkeys housed in filtered air for 2 months, no BALT was identified. After 6, 12, or 36 months, the number of BALT showed a significantly increased correlation with age in monkeys housed in filtered air. After 2 months of episodic house dust mite (HDM) exposure, no BALT was found. Monkeys exposed to HDM or HDM + ozone did not show a significant increase in BALT compared to monkeys housed in filtered air. However, monkeys exposed to ozone alone did show significant increases in BALT compared to all other groups. In particular, there were frequent accumulations of lymphocytes in the periarterial space of ozone exposed animals. In conclusion, BALT in rhesus monkeys housed under filtered air conditions is age-dependent. BALT significantly increased in monkeys exposed to ozone in comparison with monkeys exposed to HDM.

Keywords: age effects; allergen inhalation; bronchus-associated lymphoid tissue; ozone inhalation; rhesus monkey.

FIGURE 1

The house-dust-mite and ozone exposure of the monkeys (for details see Joad et al. (2008), Kajekar et al. (2007), Moore et al. (2014), Murphy et al. (2012), Schelegle et al. (2003))

FIGURE 2

Schematic drawing of the lung of rhesus monkeys

FIGURE 3

BALT in the lung of a rhesus monkey proximal part of the lung after breathing filtered air for 12 months. Insert higher magnification

FIGURE 4

BALT in the peripheral parts of the lung of a rhesus monkey breathing house-dust-mite and ozone (12 months). The insert documents the BALT at on higher magnification