BACKGROUND
nasal polyp constitutes a benign growth process in the nasal and sinus mucosa which is mainly located in the middle meatus and never in the inferior meatus.
the etiology of nasal polyps, which is a common clinical condition, is not well understood.
infections, allergy and immunological factors are considered.
histopathologically polyps surface is covered by a ciliated pseudostratified epithelium and the subepithelial area is characterized by an eosinophilic inflammation in more than 80% of cases.
the density of goblet cells in nasal polyps is much lower than in the normal nasal mucosa.
the glands of nasal polyps are long, tubular, of varying shape, size and type, and their density is more than  <dig> times lower than in nasal mucosa  <cit> .
receptor-binding cancer antigen expressed on siso cells  is a protein which has been demonstrated in various human cancer cells responsible for tumour escape from host immunological surveillance.
rcas <dig> is not only the marker of cancer process, but its expression has also been observed in physiological conditions and the development of non-neoplastic tumours  <cit> .
it has been demonstrated in the bone marrow, the endometrium, the decidua, the placenta, waldeyer's ring and immune mediated diseases.
rcas <dig> seems to be responsible for the regulation of cytotoxic cells activity  <cit> .
within waldeyer's ring rcas <dig> has been expressed by reticular epithelial cells lining the tonsils.
the reticular epithelium enables the communication between the antigen and the germinal center, which activates an immunological response  <cit> .
this role of rcas <dig> in the regulation of immune cells activity has also been confirmed in the creation of maternal immune tolerance during pregnancy.
the expression of rcas <dig> in the healthy endometrium depended on the hormonal cycle fluctuations and was related to the immune cytotoxic activity changes  <cit> .
dna fragmentation factor  is composed of a  <dig> kda protein dff <dig>  with a nuclease activity, and a  <dig> kda protein inhibitory subunit dff <dig>  <cit> .
since dff <dig> is able to interact with this nuclease as a molecular chaperone and ensures its correct folding it has been shown to be required for generating functional dff <dig> nuclease  <cit> .
it has been demonstrated that dff-45-deficient thymocytes are more resistant to programmed cell death  <cit> .
in esophageal and colon carcinoma cells characterized by an impairment of apoptosis, a decrease of dff <dig> level has also been observed  <cit> .
during apoptosis dff <dig> was described as a substrate for caspase- <dig>  dff <dig> seems to play an important role in the onset of apoptotic process by acting probably through the regulation of dna fragmentation  <cit> .
the aim of the study was to evaluate the ability to regulate the cytotoxic immune response  and to determine the resistance to apoptosis  in nasal polyps.
RESULTS
eosinophilic nasal polyps constituted almost  <dig> % of examined samples, the infiltration of lymphocytes was predominant in  <dig> % of nasal polyps and neutrophil concentration was observed in  <dig> %.
rcas <dig> expression in nasal polyps
rcas <dig> was identified in all examined tissue samples as a  <dig> kda band .
the highest rcas <dig> relative amount was identified in nasal polyps predominantly infiltrated by lymphocytes and it was statistically significantly higher than in eosinophilic nasal polyps .
the lowest rcas <dig> expression level was observed in neutrophilic nasal polyps, and it was statistically significantly lower than in eosinophilic nasal polyps  and statistically significantly lower than in lymphocytic nasal polyps .
the rcas <dig> expression was confirmed by immunohistochemistry method in all examined tissue samples.
a correlation of rcas <dig> expression between western blotting and immunohistochemistry was identified .
rcas <dig> immunoreactivity was found in superficial layer of pseudostratified ciliated epithelium covering the surface of nasal polyps .
moreover, rcas <dig> expression was also identified in macrophages of polypoid stroma .
dff <dig> expression in nasal polyps
dff <dig> expression was identified in all examined tissue samples as a  <dig> kda band .
dff <dig> expression was statistically significantly higher in eosinophilic nasal polyps in comparison to lymphocytic nasal polyps  and significantly higher in eosinophilic nasal polyps than in neutrophilic .
dff <dig> expression was at a comparable level in neutrophilic and lymphocytic nasal polyps.
the obtained results of rcas <dig>  dff- <dig> and beta-actin control protein in examined tissue samples are presented in table  <dig>
• no differences statically significant,
the fact that the amount of beta-actin in all groups of examined nasal polyps was found to be identical  indicates that the loading of protein was equal in all samples examined and allows to perform a comparative study in rcas <dig> expression between examined groups.
discussion
in the presented study statistically significant differences in rcas <dig> and dff <dig> expression in nasal polyps were identified according to the predominant immune cell infiltration type: eosinophils, lymphocytes and neutrophils.
the regulation of polypoid growth is biochemically determinated by various factors, like galectin- <dig>  known of anti-apoptotic activity, which expression is markedly higher in nasal polyps than in nasal turbinate  <cit> .
apoptosis is defined as programmed cell death.
it has been reported that apoptosis mediated through the interaction of fas and fas-l might participate in immune privilege of nasal polyps  <cit> .
fas/fas-l interactions are an important mechanism in the functional organ development and in pathological changes such as cancer and immune mediated diseases through the participation in the regulation of the activity of immune cells  <cit> .
the expression of fas-l has been identified in both nasal polyps and nasal turbinate mucosa, but has been enhanced in nasal polyps.
moreover, fas-l positive cells have been found in the down growing epithelium of nasal polyps and in the epithelial layer of cystically dilated glands  <cit> .
fas/fas-l interaction results in the activation of the caspase cascade through fadd  leading to the dff- <dig> dissociation from dff- <dig> and liberation of the dna-ase responsible for the dna fragmentation  <cit> .
ohshima compared fasl and rcas <dig> expressions in reed-sternberg cells and trophoblast cells, and revealed that both proteins activate independently fas-associated death domain which activates the caspase cascade and leads to the apoptosis of target cell.
in this way the cells expressing rcas <dig> and fas-l are responsible for suppression of immune cytotoxic lymphocytes  <cit> .
in both, fas-l and rcas <dig> pathways of apoptosis dff-45/dff- <dig> complex seems to be crucial.
in the presented study rcas <dig> immunohistochemically was identified only in the pseudostratified ciliated epithelium covering the surface of nasal polyps and this localization differs from the reported fas-l localization in nasal polyps.
rcas <dig> positive macrophages were identified in polypoid tissue stroma.
until now rcas <dig> positive macrophages have been identified in the bone marrow where they are responsible for the regulation of maturating erythroblasts  <cit> .
additionally rcas <dig> positive macrophages have been found in ovarian endometriosis although they have not been present in the normal, eutopic endometrium  <cit> .
in sum, it might be interpreted that rcas <dig> positive macrophages might participate in the local immune dysfunction in nasal polyps.
the inflammatory infiltrate of nasal polyps consists of eosinophils, lymphocytes, mast cells, macrophage-like cd68+ cells  <cit> .
both eosinophils and lymphocytes are resistant to fas-l/fas mediated apoptosis  <cit> .
the lymphocytes that infiltrate nasal polyps have been defined to be predominantly memory t cells in an activated status and produced a mixed th1/th <dig> cytokine pattern   <cit> .
cytokines, including il- <dig>  ifn-gamma, gm-csf also participate in delaying of the death process in these cells, thus contributing to developing of tissue and blood eosinophilia  <cit> .
the lymphocytes infiltrated nasal polyps in our study were characterized by the highest rcas <dig> expression level and a statistically significantly lower dff- <dig> expression than eosinophilic nasal polyps.
low dff- <dig> level might indicate that the polyps infiltrated by lymphocytes are more resistant to immune mediated apoptosis than eosinophilic nasal polyps.
additionally, the expression of rcas <dig>  a factor participating in the suppression of cytotoxic activity, might help polypoid tissue to avoid immune cytotoxicity.
the etiology of neutrophilic nasal polyps is connected with bacterial inflammation.
it has been postulated that superantigens derived mainly from staphylococcus aureus might be potent activators of t cells and might therefore participate in the formation of nasal polyps  <cit> .
superantigens are able to activate the immune cytotoxic response without antigen presenting cells which results in the exposure of polypoid tissue to immune mediated apoptosis.
in our study neutrophilic nasal polyps were characterized by a comparable level of dff- <dig> as lymphocytic nasal polyps and lower than eosinophilic nasal polyps.
we suspect that neutrophilic nasal polyps, similarly to lymphocytic nasal polyps, are more resistant to immune mediated apoptosis than eosinophilic nasal polyps, which might compensate the immune cytotoxicity.
the observed decreased rcas <dig> expression in neutrophilic nasal polyps might result from the immune cells infiltration pattern.
CONCLUSIONS
the changes in dff- <dig> level in nasal polyps regarding the type of immune cell infiltration might indicate a different resistance to apoptosis mediated by immune cells.
the alterations in rcas <dig> expression indicate that nasal polyps have the ability to regulate the cytotoxic immune response.

 nasal polyp constitutes a benign growth process in the nasal and sinus mucosa which is mainly located in the middle meatus and never in the inferior meatus. the etiology of nasal polyps, which is a common clinical condition, is not well understood. infections, allergy and immunological factors are considered. histopathologically polyps surface is covered by a ciliated pseudostratified epithelium and the subepithelial area is characterized by an eosinophilic inflammation in more than 80% of cases. the density of goblet cells in nasal polyps is much lower than in the normal nasal mucosa. the glands of nasal polyps are long, tubular, of varying shape, size and type, and their density is more than times lower than in nasal mucosa. receptor-binding cancer antigen expressed on siso cells is a protein which has been demonstrated in various human cancer cells responsible for tumour escape from host immunological surveillance. rcas is not only the marker of cancer process, but its expression has also been observed in physiological conditions and the development of non-neoplastic tumours. it has been demonstrated in the bone marrow, the endometrium, the decidua, the placenta, waldeyer's ring and immune mediated diseases. rcas seems to be responsible for the regulation of cytotoxic cells activity. within waldeyer's ring rcas has been expressed by reticular epithelial cells lining the tonsils. the reticular epithelium enables the communication between the antigen and the germinal center, which activates an immunological response. this role of rcas in the regulation of immune cells activity has also been confirmed in the creation of maternal immune tolerance during pregnancy. the expression of rcas in the healthy endometrium depended on the hormonal cycle fluctuations and was related to the immune cytotoxic activity changes. dna fragmentation factor is composed of a kda protein dff with a nuclease activity, and a kda protein inhibitory subunit dff. since dff is able to interact with this nuclease as a molecular chaperone and ensures its correct folding it has been shown to be required for generating functional dff nuclease. it has been demonstrated that dff-45-deficient thymocytes are more resistant to programmed cell death. in esophageal and colon carcinoma cells characterized by an impairment of apoptosis, a decrease of dff level has also been observed. during apoptosis dff was described as a substrate for caspase- dff seems to play an important role in the onset of apoptotic process by acting probably through the regulation of dna fragmentation. the aim of the study was to evaluate the ability to regulate the cytotoxic immune response and to determine the resistance to apoptosis in nasal polyps.  eosinophilic nasal polyps constituted almost % of examined samples, the infiltration of lymphocytes was predominant in % of nasal polyps and neutrophil concentration was observed in %. rcas expression in nasal polyps rcas was identified in all examined tissue samples as a kda band. the highest rcas relative amount was identified in nasal polyps predominantly infiltrated by lymphocytes and it was statistically significantly higher than in eosinophilic nasal polyps. the lowest rcas expression level was observed in neutrophilic nasal polyps, and it was statistically significantly lower than in eosinophilic nasal polyps and statistically significantly lower than in lymphocytic nasal polyps. the rcas expression was confirmed by immunohistochemistry method in all examined tissue samples. a correlation of rcas expression between western blotting and immunohistochemistry was identified. rcas immunoreactivity was found in superficial layer of pseudostratified ciliated epithelium covering the surface of nasal polyps. moreover, rcas expression was also identified in macrophages of polypoid stroma. dff expression in nasal polyps dff expression was identified in all examined tissue samples as a kda band. dff expression was statistically significantly higher in eosinophilic nasal polyps in comparison to lymphocytic nasal polyps and significantly higher in eosinophilic nasal polyps than in neutrophilic. dff expression was at a comparable level in neutrophilic and lymphocytic nasal polyps. the obtained results of rcas dff- and beta-actin control protein in examined tissue samples are presented in table • no differences statically significant, the fact that the amount of beta-actin in all groups of examined nasal polyps was found to be identical indicates that the loading of protein was equal in all samples examined and allows to perform a comparative study in rcas expression between examined groups. discussion in the presented study statistically significant differences in rcas and dff expression in nasal polyps were identified according to the predominant immune cell infiltration type: eosinophils, lymphocytes and neutrophils. the regulation of polypoid growth is biochemically determinated by various factors, like galectin- known of anti-apoptotic activity, which expression is markedly higher in nasal polyps than in nasal turbinate. apoptosis is defined as programmed cell death. it has been reported that apoptosis mediated through the interaction of fas and fas-l might participate in immune privilege of nasal polyps. fas/fas-l interactions are an important mechanism in the functional organ development and in pathological changes such as cancer and immune mediated diseases through the participation in the regulation of the activity of immune cells. the expression of fas-l has been identified in both nasal polyps and nasal turbinate mucosa, but has been enhanced in nasal polyps. moreover, fas-l positive cells have been found in the down growing epithelium of nasal polyps and in the epithelial layer of cystically dilated glands. fas/fas-l interaction results in the activation of the caspase cascade through fadd leading to the dff- dissociation from dff- and liberation of the dna-ase responsible for the dna fragmentation. ohshima compared fasl and rcas expressions in reed-sternberg cells and trophoblast cells, and revealed that both proteins activate independently fas-associated death domain which activates the caspase cascade and leads to the apoptosis of target cell. in this way the cells expressing rcas and fas-l are responsible for suppression of immune cytotoxic lymphocytes. in both, fas-l and rcas pathways of apoptosis dff-45/dff- complex seems to be crucial. in the presented study rcas immunohistochemically was identified only in the pseudostratified ciliated epithelium covering the surface of nasal polyps and this localization differs from the reported fas-l localization in nasal polyps. rcas positive macrophages were identified in polypoid tissue stroma. until now rcas positive macrophages have been identified in the bone marrow where they are responsible for the regulation of maturating erythroblasts. additionally rcas positive macrophages have been found in ovarian endometriosis although they have not been present in the normal, eutopic endometrium. in sum, it might be interpreted that rcas positive macrophages might participate in the local immune dysfunction in nasal polyps. the inflammatory infiltrate of nasal polyps consists of eosinophils, lymphocytes, mast cells, macrophage-like cd68+ cells. both eosinophils and lymphocytes are resistant to fas-l/fas mediated apoptosis. the lymphocytes that infiltrate nasal polyps have been defined to be predominantly memory t cells in an activated status and produced a mixed th1/th cytokine pattern. cytokines, including il- ifn-gamma, gm-csf also participate in delaying of the death process in these cells, thus contributing to developing of tissue and blood eosinophilia. the lymphocytes infiltrated nasal polyps in our study were characterized by the highest rcas expression level and a statistically significantly lower dff- expression than eosinophilic nasal polyps. low dff- level might indicate that the polyps infiltrated by lymphocytes are more resistant to immune mediated apoptosis than eosinophilic nasal polyps. additionally, the expression of rcas a factor participating in the suppression of cytotoxic activity, might help polypoid tissue to avoid immune cytotoxicity. the etiology of neutrophilic nasal polyps is connected with bacterial inflammation. it has been postulated that superantigens derived mainly from staphylococcus aureus might be potent activators of t cells and might therefore participate in the formation of nasal polyps. superantigens are able to activate the immune cytotoxic response without antigen presenting cells which results in the exposure of polypoid tissue to immune mediated apoptosis. in our study neutrophilic nasal polyps were characterized by a comparable level of dff- as lymphocytic nasal polyps and lower than eosinophilic nasal polyps. we suspect that neutrophilic nasal polyps, similarly to lymphocytic nasal polyps, are more resistant to immune mediated apoptosis than eosinophilic nasal polyps, which might compensate the immune cytotoxicity. the observed decreased rcas expression in neutrophilic nasal polyps might result from the immune cells infiltration pattern.  the changes in dff- level in nasal polyps regarding the type of immune cell infiltration might indicate a different resistance to apoptosis mediated by immune cells. the alterations in rcas expression indicate that nasal polyps have the ability to regulate the cytotoxic immune response. 
dff has been described as a substrate for caspase- dff seems to play an important role in the onset of apoptotic process by acting probably through the regulation of dna fragmentation. rcas is a protein expressed mainly by various human cancer cells. it is not only the marker of cancer process and its expression can also be observed in physiological processes. the aim of the study was to evaluate the ability of nasal polyps to regulate the cytotoxic immune response and to determine their resistance to apoptosis. the alterations in rcas expression indicate that nasal polyps have the ability to regulate the cytotoxic immune response. nasal polyp constitutes a benign growth process in the nasal and sinus mucosa. the higher rcas level was identified in lymphocytic nasal polyps, the medium one in eosinophilic while the lowest was identified in neutrophilic. dff- expression was higher in eosinophilic than in neutrophilic and lymphocytic nasal polyps. the changes in dff- level in nasal polyps might indicate a different resistance to apoptosis mediated by immune cells. the breaking of resistance to immune mediated apoptosis in nasal polyps might have a new therapeutic impact. it is responsible for the regulation of immune cells activity.
 nasal polyp constitutes a benign growth process in the nasal and sinus mucosa. rcas is a protein expressed mainly by various human cancer cells. it is not only the marker of cancer process and its expression can also be observed in physiological processes. it is responsible for the regulation of immune cells activity. dff has been described as a substrate for caspase- dff seems to play an important role in the onset of apoptotic process by acting probably through the regulation of dna fragmentation. the aim of the study was to evaluate the ability of nasal polyps to regulate the cytotoxic immune response and to determine their resistance to apoptosis.  the higher rcas level was identified in lymphocytic nasal polyps, the medium one in eosinophilic while the lowest was identified in neutrophilic. dff- expression was higher in eosinophilic than in neutrophilic and lymphocytic nasal polyps.  the changes in dff- level in nasal polyps might indicate a different resistance to apoptosis mediated by immune cells. the alterations in rcas expression indicate that nasal polyps have the ability to regulate the cytotoxic immune response. the breaking of resistance to immune mediated apoptosis in nasal polyps might have a new therapeutic impact. 