Beryllium - Toxicology of Metals - page 417

ovary cells (Brooks, 1989) and in hamster lung cells
(Ashby et al ., 1990). Larramedy et al . (1981) found
increased sister chromatid exchange (SCE) in HEC
cells and cultured human lymphocytes after treatment
with beryllium sulfate. Dose-dependent increases
in SCE were also observed with both beryllium
chloride and beryllium nitrate-exposed V79 cells
(Kuroda et al ., 1991). On the other hand, no increase
in SCE by beryllium sulfate treatment of human
lymphocytes or the cultured macrophage cell line
was found by Anderson (1983).
Soluble beryllium compounds seem to be weakly
genotoxic (Toxicological Profi le, 2002). In the occupa-
tional settings, workers are exposed predominantly to
beryllium as inhalable particles, and adverse effects
of beryllium depend on the chemical species and sur-
face properties of particles. According to Gordon and
Browser (2003), it would be useful to reexamine the
mechanisms of the mutagenic activity of beryllium
using relevant chemical forms of beryllium.

The T-cell-mediated process is orchestrated by
cytokines. Tinkle et al . (1997) reported that Be-stimulated
cells from BALF of CBD subjects produce high levels of
IFN

protein and mRNA with a transient increase in IL-
2 protein and mRNA production. Be-stimulated BALF
cells obtained from healthy donors did not produce these
cytokines. Macrophages isolated from BALF of sarcoido-
sis and CBD patients had signifi cantly elevated levels of
TNFa mRNA (Bost et al ., 1994). Be-stimulated CBD BALF
cells also produce TNFa, IL-6 (Tinkle et al ., 1997), and
IL-10 (Tinkle et al ., 1999). IL-10 inhibits antigen-induced
T-cell proliferation in many infl ammatory diseases, but
it had no effect on Be-stimulated T-cell proliferation
(Tinkle et al ., 1999). Moreover, recombinant IL-4 did not
down-regulate beryllium-stimulated cytokines in CBD
(Maier et al ., 2001). Be-stimulated CD4 + T-cell prolifera-
tion and TNF

γ

production is blocked by anti-HLA-DP
monoclonal antibodies (Parsons et al ., 2002). The data
show that Be-stimulated CD4 + T-cell proliferation and
production of proinfl ammatory cytokines are medi-
ated primarily by HLA-DP.

α

7.5 Mechanisms of Toxic Action
Chronic beryllium disease is a T-cell-mediated dis-
order. Beryllium, acting as a hapten, interacts with the
antigen-presenting cells in the lungs. Beryllium peptide
associated with major histocompatibility (MHC) class
II molecule is recognized by the T-cell receptor with the
help of CD4 + molecules (Newman, 1996a; Saltini et al .,
1989). This interaction triggers CD4 + T lymphocytes acti-
vation and proliferation. Only certain HLA-DP molecules
allow Be-antigen presentation to Be-specifi c CD4 + T-cell
clones. Some authors suggest that particular amino acid
residues, for example at positions 55-56 and/or 69 of the
DPß-chain, are required for Be-antigen presentation in
most Be-sensitized and CBD individuals (Fontenot et al .,
2001). Beryllium-specifi c CD4 + T cells were found in the
peripheral blood and in bronchoalveolar lavage fl uid
(BALF) from individuals with the disease (Maier and
Newman, 1998; Mroz et al ., 1991, Newman, 1996b). These
cells proliferate in the BeLPT. Their accumulation in large
numbers (up to 29% of the BALF cells) is associated with
the development of granulomatous infl ammation in the
lung of CBD patients (Fontenot et al ., 2002). Fontenot et al .
reported that a number of individuals with CBD revealed
an increase in the percentage of T-cell receptor (TCR) vari-
able ß3 regions (Vß3) in BALF (Fontenot et al ., 1998; 1999).
These expansions are composed of oligoclonal popula-
tions of T cells with related complementary determining
region 3 (CDR3) with invariant aspartic acid (D) at the
96 th position of the ß-chain and length of 7-8 amino acids
in some individuals. These fi ndings suggest that in CBD,
the pathogenic T-cell population are CD4 + T cells with
CDR3 motif.

7.6 Biomarkers of Effect
The beryllium blood lymphocyte proliferation
test (BLTP) is used as a medical surveillance tool
for assessment of persons at risk for developing
clinical and subclinical chronic beryllium disease
(Kreiss, 1977; Newman et al ., 1989; Rossman et al .,
1988). It serves to detect sensitization to beryllium
both in asymptomatic persons sensitized and those
with CBD. It is commonly used not only in the diag-
nostics but also in workplace surveillance. It is also
regarded as exposure marker for exposures from 8
weeks to 30 years before the testing; however, its
negative result is not the evidence for the absence of
beryllium exposure.
During the analytical procedure, lymphocytes are at
fi rst incubated in a mixture containing beryllium salt,
usually BeSO 4 . After incubation, 3 H-thymidine (3H-
TdR) is added to the mixture. The amount of 3 H-TdR
taken up by the lymphocytes refl ects lymphocyte acti-
vation expressed as counts per minute (cpm). The test
is replicated six times, using three concentrations of
BeSO 4 . The response is expressed as a stimulation index
(SI) where

cmp of cultures with beryllium sulfate

SI =

cmp of cultures without beryllium sulfate

In 1995, the participants of a workshop organized
by the Beryllium Industry Scientifi c Advisory Com-
mittee (BISAC) and representatives of fi ve laboratories