Health Assessment Document for Diesel Emissions - NSCEP | US ...

1 with matched controls for the number of B and T lymphocytes and null cells isolated from the
2 tracheobronchial lymph nodes, spleen, and blood. Cell viability as measured by trypan blue
3 exclusion was comparable between the exposed and control groups. The results of this study and
4 others on the effects of exposure to diesel exhaust on the immune system are summarized in.
· 5 Dible 5-8.
6 Mentnech et al. (1984) examined the effect of diesel exhaust on the immune system of
7 rats. Exposures were to 2 mg/m 3 DPM for 7 h/day, 5 days/week for up to 2 years. Rats exposed
8 for 12 and 24 mo weretested for immunocompetency by determining '!lltibody-producing cells
9 in the spleen 4 days after immunization with sheep erythrocytes. The proliferative response of
1 0 splenic T -lymphocytes to the mitogens concanavalin A and phytohemagglutinin was assessed in
11 rats exposed for 24 mo. There were no significant differences between the exposed and control
12 animals. Results obtained from these two assays indicate that neither humoral immunity
13 (assessed by enumerating antibody-producing cells) nor cellular immunity (assessed by the
14 lymphocyte blast transformation assay) were markedly affected by the exposures.
15 Bice et al. ( 1985) evaluated whether or not exposure to diesel exhaust would alter
16 antibody immune responses induced after lung immunization of rats and mice. Exposures were
17 to 0.35, 3.5, or 7.1 mg/m 3 DPM for 7 h/day, 5 days/week for 24 mo. Chamber controls and
18 exposed animals were immunized by intratracheal instillation of sheep red blood cells (SRBC)
. .
19 after 6, 12, 18, or 24 mo of exposure. No suppression in the immune response occurred in either
20 species. After 12, 18, and 24 mo of exposure, the total number of anti-SRBC IgM antibody
21 forming cells (AFCs) was elevated in rats, but not in mice, exposed to 3.5 or 7.1 mg/m 3 DPM;
· 22 after 6 mo of exposure, only the 7.1 mg/m 3 level was found to have caused this response in rats.
23 The number of AFC per 10 6 lymphoid cells in lung-associated lymph nodes and the levels of
24 specific IgM, IgG, or IgA in rat sera were not significantly altered. The investigators concluded
25 that the increased cellularity and the presence ofDPM in the lung-associated lymph nodes had
26 only a minimal effect on the immune and antigen filtration function of these tissues. Takafuji et
27 al. (1987) evaluated the IgE antibody response of mice inoculated intranasally at intervals of 3
28 weeks with varying doses of a suspension ofDPM in ovalbumin.
29 Antiovalbumin IgE antibody titers, assayed by passive cutaneous anaphylaxis, were
30 enhanced by doses as low as 1 J.lg of particles compared with immunization with ovalbumin
31 alone.
32 The inhalation of diesel exhaust appeared to have only minimal effects on the immune
33 status of rats and guinea pigs. Conversely, intranasally delivered doses as low as 1 J.lg ofDPM
· 34 exerted an adjuvant activity for IgE antibody production in mice. Further studies of the effects of
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