the molecular cloning of novel nk receptors ( nkrs ) was reported 
 [ 13 ] , and it was subsequently shown that the receptors transmit negative signals [ 4 , 5 ] . in human , nkrs can be divided into 3 classes : immunoglobulin ( ig)-like receptors , 
 including killer cell ig - like receptors ( kirs ) and leukocyte 
 ig - like receptors ( lirs ) , lectine - like receptors ( cd94/nkg ) , and 
 natural cytotoxicity receptors ( ncrs ) , including nkp30 , nkp44 , 
 and nkp46 . kirs are expressed on many nk cells and on subpopulations of 
 t - cells , and have been implicated in autoimmune 
 conditions such as rheumatoid arthritis ( ra ) [ 8 , 9 ] and scleroderma , where associations have been found with 
 3-domain kirs ( kir2dl1 , 2 , and 3 ) known to recognize hla - c 
 alleles [ 11 , 12 ] . we have also demonstrated that the expression of kir2dl1 on cd8 + t cells was reduced in patients with ra compared to healthy subjects , and that the upregulation of 
 kir2dl1 , 2 , and 3 by treatment with il-2 was weaker in ra 
 patients than in healthy subjects . low kir expression on cd8 + t cells in ra might be associated with the mechanism of 
 self - attacking characteristics of autoimmune diseases . also , the 
 low response of kirs to il-2 suggests that patients with ra 
 might be highly susceptible to mycobacterium tuberculosis 
 ( tb ) . based on these findings , it is considered that the status of 
 kir expression may be involved in the pathogenesis of ra as well 
 as susceptibility to microbes such as tb . therefore , the disturbance of kir expression in ra 
 raises an interesting question : does kir expression on peripheral 
 lymphocytes in patients with ra change with disease activity or 
 not ? however , changes in kir expression on lymphocytes have not 
 yet been analyzed in ra patients . here , we measured kir expression on lymphocytes in patients with 
 ra , and assessed the correlation between kir expression and 
 disease activity and changes in kir expression during the disease 
 course . fifteen patients ( 9 females and 6 males ) with flares of ra as 
 defined by the revised criteria of the american college of 
 rheumatology   were included in this study . the 
 characteristics of these patients were as follows : mean  sd age of 
 62.0  9.4 years ( range : 4272 ) , mean  sd disease duration of 8.1  6.2 years ( range : 224 ) , mean  sd esr ( erythrocyte sedimentation rate ) 48  35 mm / h ( range : 2886 ) , mean  sd ch50 ( serum complement titer/50% hemolytic unit of complement ) 36.9  7.0 u / ml ( range : 2852 ) , 
 anatomical stage   2.2  1.4 , and functional class 
 2.1  0.5 . all were receiving nonsteroidal anti - inflammatory 
 drugs ( nsaids ) . two were also taking bucillamine , 7 
 salazosulfapyridine , and 4 prednisolone ( psl , 
 2.57.5 mg / day ) . fluorescein - isothiocyanate ( fitc)-conjugated antihuman cd16 , 
 phycoerythrin ( pe)-conjugated antihuman cd158a ( eb6 ) , and 
 pe - conjugated antihuman cd158b ( gl183 ) were purchased from 
 immunotech , marseille , france . antibody eb6 reacts with kir2dl1 
 and kir2ds1 , and gl183 reacts with kir2dl2 , kir2dl3 , and 
 kir2ds2 [ 11 , 12 ] . peripheral blood mononuclear cells ( pbmcs ) obtained from patients 
 with ra were separated from heparinized blood by lymphoprep 
 ( nyegaard , oslo , norway ) gradient centrifugation 
 . each pbmc was incubated in a culture dish in a 
 humidified 5% co2/95% air atmosphere at 37c for 60 minutes . these cell suspensions were washed twice in 
 phosphate - buffered saline ( pbs ) . surface phenotyping was carried out using a two - color 
 immunofluorescence staining technique , with isotype - specific mouse 
 antihuman antibody conjugated with either fitc or pe . each sample of stained cells was suspended in 0.5 ml of pbs 
 and analyzed by flow cytometry . lymphocyte subsets were identified 
 by gating analysis , and fluorescence profiles were obtained for 
 10000 cells from each sample . negative controls for each 
 experiment were performed with fitc- and pe - labeled mouse 
 immunoglobulin - g ( ig - g ) . all data were collected 
 in a computer database and analyzed using the statview - j 4.02 
 program ( abacus concept , berkeley , calif , usa ) . the mann - whitney 
 u test was performed for each set of the surface antigen . for 
 all statistical tests , the correlation between the counts of kir - expressing cells and 
 disease activity in ra . the correlation between cd158a / b - expressing cells and crp , esr , 
 and igm - rheumatoid factor ( igm - rf ) is summarized in 
 table 1 . there was no correlation between the counts 
 of cd158a - expressing cells and disease activity , although there 
 was a tendency towards a correlation between cd158a - expressing 
 cells and esr . also , the counts of cd158b - expressing cells did not 
 correlate with classical inflammatory parameters ( crp : c - reactive 
 protein , and esr ) and igm - rf . the changes of cd158a- and cd158b - expressing cells during the 
 followup of 3 months . figure 1 shows the changes in the populations of cells expressing cd158a ( figure 1(a ) ) and cd158b 
 ( figure 1(b ) ) during the followup of 3 months . ten 
 of the ra patients did not show changes in the expression of 
 cd158a and cd158b . two patients showed an expansion of the 
 populations of both cd158a- and cd158b - expressing cells . in 
 contrast , 3 patients showed decrease in the populations of both 
 cd158a- and cd158b - expressing cells . however , time - related changes 
 in the expression of cd158a / b were independent from those of 
 inflammation parameters and igm - rf in the 5 cases 
 ( figure 1 ) . additionally , there were no differences in 
 clinical features among the three groups : ( i ) patients with no 
 changes in kir expression , ( ii ) patients with a decrease in kir 
 expression , and ( iii ) patients with an increase in kir expression 
 ( data not shown ) . the biological functions of kirs have been thoroughly 
 investigated . in brief , nk cell function is generally regulated by 
 a balance between signals transmitted by inhibitory and 
 stimulatory receptors . ligand binding to inhibitory receptors 
 recruits phosphatases that dephosphorylate downstream activation 
 proteins , thereby terminating the activating - signaling pathway . thus , activation of nk cell function occurs when there is a net 
 excess of stimulatory over inhibitory signals . recent studies have demonstrated findings supporting the important 
 functions of nk cells in regulating autoimmunity . we have also demonstrated that the population of cd8+cd158a+ 
 cells was reduced in patients with ra compared to healthy subjects 
 . similarly , nakiri et al have reported that among 
 patients with ra , nkb1+cd8 + t cells decreased significantly in 
 comparison to controls . it is considered that the low population of kir - expressing cells in t cells might be associated 
 with the mechanism of self - attacking characteristics of autoimmune 
 diseases , and that an unnatural expression of kirs may contribute 
 to the pathogenesis of ra . however , it has not been demonstrated 
 whether kir expression correlates with disease activity in 
 ra . as far as we know , this is the first report to assess the 
 correlation between kir expression and disease activity . in this 
 study , we did not find a significant relationship between cd158a / b 
 expression on peripheral lymphocytes , classical inflammatory 
 parameters ( crp and esr ) , and igm - rf . these findings suggest 
 that unnatural kir expression contributes to one of the triggers 
 of ra pathogenesis , but not a recruitment of chronic inflammation 
 to induce joint damage . other investigators have revealed that the 
 kir2ds2 gene was significantly enriched among patients with 
 vasculitis in ra . furthermore , we have observed the changes in the population of 
 cd158a / b - expressing cells . in this followup , time - related changes 
 in the population of kir - expressing cells were independent from 
 those of inflammation parameters and igm - rf . additionally , the 
 patients were divided into 3 groups according to the pattern of 
 changes in the population of kir - expressing cells . however , there 
 was no difference in the clinical features among the 3 groups : ( i ) 
 patients with no changes in kir expression , ( ii ) patients with a 
 decrease in kir expression , and ( iii ) patients with an increase in 
 kir expression . we also did not find any correlation in the 
 disease activity between these 3 groups . these findings may also 
 suggest that unnatural kir expression contributes to one of the 
 triggers of ra pathogenesis , but not a recruitment of chronic 
 inflammation to induce joint damage . to support this hypothesis , 
 further analysis of kir expression on the cells of several 
 lineages finally , there was no correlation between kir expression and 
 disease activity ; therefore , the clinical use of kir expression 
 should be limited , while unnatural kir expression may be involved 
 in the pathogenesis of ra , but not a recruitment of chronic 
 inflammation to induce joint damage .
objective . 
 the genes for killer - cell immunoglobulin - like receptors ( kirs ) have been cloned and their functions and expression in patients with rheumatoid arthritis ( ra ) have been partially clarified . 
 however , the correlation between their expression and disease activity has not been analyzed in patients with ra . 
 thus , we measured kir expression on lymphocytes in patients with ra , and assessed the correlation between kir expression and disease activity . 
 patients and methods . in the cross - sectional study , 15 patients ( 9 females and 6 males ) who fulfilled the diagnostic criteria for ra were assessed . in the longitudinal study , 
 patients who were followed - up for 3 months were assessed . 
 cd158a / b expression on peripheral blood mononuclear cells ( pbmc ) of ra patients was analyzed using flow cytometry . 
 results . 
 no significant correlation between kir expression and crp , esr , or igm - rf was observed . 
 there was no remarkable change in the expression of kirs between the baseline and after 3 months . 
 additionally , in the 5 patients whose expression of kirs particularly changed , the time - related changes in the expression of kirs were independent from those of inflammation parameters and igm - rf . 
 conclusion . 
 there was no correlation between kir expression and disease activity ; therefore , the clinical use of kir expression should be limited , while unnatural kir expression may be involved in the pathogenesis of ra , but not a recruitment of chronic inflammation to induce joint damage .