Table 4.

Fc receptors and cartilage damage in knee joints of mice during immune-complex-mediated arthritis

		Mouse strain
Index of cartilage damage	Day	FcRγ-/-	C57BL/6	DBA/1
PG depletion†	1	0	0.2 ± 0.1	ND
	3	0.1 ± 0.1*	2.2 ± 0.5	2.8 ± 0.3*
	7	ND	1.5 ± 0.4	3.0 ± 0*
	14	ND	0.6 ± 0.4	3.0 ± 0*
Chondrocyte death (%)‡	1	0	0	ND
	3	0	18 ± 6	35 ± 12
	7	ND	20 ± 10	68 ± 24*
	14	ND	20 ± 9	98 ± 5*
Matrix erosion§	1	0	0	ND
	3	0	0	0.4 ± 0.3
	7	ND	0.2 ± 0.2	1.5 ± 0.7*
	14	ND	0.2 ± 0.2	2.3 ± 0.6*

Cartilage damage was assed using total knee-joint sections stained with safranin O (for PG depletion and matrix erosion) or H&E (for chondrocyte death). PG depletion was absent in FcRγ^-/-, moderate in C57BL/6, and high in DBA/1 mice. Irreversible cartilage damage, chondrocyte death, and erosion of the cartilage matrix, were almost absent in both FcRγ^-/- and their control C57BL/6 mice, whereas erosion in DBA/1 mice was massive. To evaluate significance, the Mann-Whitney U-test (^*P < 0.05) was used. ^†Scored by two blinded, independent observers. 1 = mild, 2 = moderate, 3 = maximal destaining of cartilage. ^‡ Scored by two blinded, independent observers, as the percentage of total cartilage area in the surface layer (up to the tide mark) containing empty lacunae. ^§Measured by determining the area in the cartilage surface layer (up to the tide mark) that had been lost during arthritis by two blinded observers, and expressed using an arbitrary score from 0–3 (0 = no; 1 = minor (0-10%); 2 = moderate (>10-50%); 3 = maximal (>50-100%). ND = Not done.