A T-dependent antibody response evaluation in CD-1 mice after an acute whole-body inhalation exposure to nickel (II) chloride hexahydrate

Figures & data

Table 1. Organ weights at terminal necropsy and body weights from Day 1 to Day 6.

	Group 1	^aGroup 2	^aGroup 3	^aGroup 4	Group 5
	(Negative control)	(20 µg Ni/m^3)	(50 µg Ni/m^3)	(100 µg Ni/m^3)	(Positive control)
Liver weight (g)	1.44 ± 0.04	1.49 ± 0.04	1.49 ± 0.02	1.51 ± 0.03	1.43 ± 0.04
Spleen weight (g)	0.13 ± 0.01	0.14 ± 0.01	0.14 ± 0.01	0.14 ± 0.01	**0.08 ± 0.00
Thymus weight (g)	0.05 ± 0.00	0.06 ± 0.01	0.05 ± 0.00	0.05 ± 0.00	**0.02 ± 0.00
Body weight (g)
Day 1	30.56 ± 0.36	30.72 ± 0.37	30.95 ± 0.22	30.71 ± 0.40	30.39 ± 0.44
Day 2	29.17 ± 0.28	29.35 ± 0.36	29.88 ± 0.30	29.30 ± 0.47	29.87 ± 0.33
Day 3	29.25 ± 0.38	29.69 ± 0.31	29.89 ± 0.29	30.31 ± 0.50	30.21 ± 0.28
Day 4	29.41 ± 0.39	29.97 ± 0.32	30.19 ± 0.23	30.42 ± 0.47	29.76 ± 0.36
Day 5	29.34 ± 0.34	30.45 ± 0.35	30.79 ± 0.30	31.08 ± 0.51	29.43 ± 0.32
Day 6	29.49 ± 0.35	30.51 ± 0.27	30.92 ± 0.26	30.91 ± 0.58	29.36 ± 0.18

^aNominal exposure concentration listed.

**p ≤ 0.01 vs. Group 1.

Table 2. ^aGravimetric concentrations, nickel concentrations and aerosol particle size.

Group	Target concentration		^bMean analyzed µg Ni/m^3	Mean MMAD (µm)	Mean GSD
	µg Ni/m^3	µg NiCl2.•6H2O/m^3
1	0	0	<0.1	–	–
2	20	81	16.0 ± 1.5	0.7	3.33
3	50	203	44.1 ± 4.6	1.0	3.46
4	100	405	80.9 ± 12.4	1.1	2.96

^aFor the filter from exposure chamber 1 (Group 1), Ni content was <0.5 µg/filter. For chambers 2 (Group 2), 3 (Group 3) and 4 (Group 4) filter samples, Ni contents were, respectively, 101.7 [± 6.4] µg/filter (N = 2), 163.3 [± 10.4] µg/filter (N = 3), and 207.0 [± 14.9] µg/filter (N = 5).

^bValues reported as mean ± SD (standard deviation)

Figure 1. Individual IgM antibody-forming cell responses to SRBC in female CD-1 mice following 24-hr whole-body inhalation exposure to nickel chloride hexahydrate. (A) Inter-leaved scatter with bars of individual spleen cell numbers in vehicle control, nominal nickel chloride hexahydrate treatment groups, and positive control (CP). (B) Inter-leaved scatter with bars of individual Total Spleen Activity [IgM AFC/spleen (10³)] values. (C) Inter-leaved scatter with bars of individual Specific Activity [IgM AFC/spleen cells (10⁶)] responses to SRBC on Day 4 after exposure. Scatter plots: biological variability of the responses in outbred mice, with low and high responders even in controls. N = 10 mice/group. *p < 0.05; **p < 0.01 vs. control (Group 1).

Table 3. Summary of immunotoxicity findings in mice with 24-hr exposure to NiCl_2·6H₂O.

Endpoint	Groups (nominal exposure in µg Ni/m^3)				Cyclophosphamide
	0^a	20	50	100
Spleen cells (× 10^7)	4.55 ± 0.35	4.22 ± 0.15 [−7.3]	3.86 ± 0.19 [−15.2]	**3.07 ± 0.27 [−32.5]	**1.54 ± 0.36 [−66.2]
Total spleen activity IgM AFC/spleen (× 10^3)	175.22 ± 24.41	**311.70 ± 29.01 [78.3]	202.20 ± 19.51 [15.4]	**282.10 ± 27.74 [61.1]	**0.00 [−100.0]
Specific activity IgM AFC/10^6 spleen cells	1365.11 ± 225.18	**2510.30 ± 250.62 [83.9]	1763.80 ± 180.64 [29.2]	**3239.10 ± 430.50 [137.3]	**0.00 [−100.0]

^aNegative control. Female mice were exposed to filtered air. A Grubb’s test for outliers identified one control mouse with an unusually higher number of spleen cells (animal thus excluded from analyses).

Values in brackets represent percent difference from negative control group.

N = 10, unless otherwise noted.

**p < 0.01 vs Group 1.