dendritic cells ( dcs ) are non - lymphoid antigen - presenting cells distributed widely throughout the body and are distinguishable from macrophages by their lack of both phagocytic activity and capacity to act as effectors cells . morphologically , they present a complex of dendritic cytoplasmic projections , one or more lobulated nucleoli , clear cytoplasm with scattered organelles and lack of both phagocytic activity and capacity to act as effectors cells . t - cell associated dcs include the interdigitating dendritic cells ( idcs ) , indeterminate cells , langerhans cells , connective tissue dendritic cells and veiled cells ( dendritic leukocytes)9,22,23 . fdcs are located in b - cell dependent areas of the lymphoid follicles of secondary lymphoid organs . functionally , they have an ability to bind and retain antigens through linking complement and immune complexes for a long time , and are involved in b - cell proliferation , selection and differentiation18,21 . fdcs can be stained through the complement receptors , c3d ( cd21 ) and c3b ( cd35 ) , and by the low affinity to ige receptor ( cd23 ) . also , fdcs are immunopositive to cell cycle markers , fdcs - associated antigen ( dcr-1 ; ki - m4 ; cna.42 ; dr53 ) , intermediated filament , adhesion molecules , cytokine receptors and to calcium - bindings proteins ( calmodulin ; caldesmon ; annexin ii ; annexin vi and s100 protein -subunit ) . the immunophenotype , as well as ultrastructural features , of fdcs are variable depending on their distribution in the zones of lymphoid follicles . idcs are located in the t - cell areas of lymph node , spleen , and thymus , and are related to the function of presenting antigens to t - cells . in contrast to langerhans cells , idcs are immunonegative to cd1a5,20 . due to the relationship between fdcs / b - cell and idcs / t - cell , the microenvironment of the neoplastic or reactive transformation of b- and t - cell produce alterations in expression of dendritic cells types . also , a comprehensive investigation on this subject might provide valuable information about diagnosis of lymphomas1,3,7,12,14,17,24 . the goal of this study was to evaluate the presence and distribution of fdcs and idcs in oral lymphomas . the experimental protocol was approved by the committee of bioethics in research of the dental school of the university of so paulo , so paulo , sp , brazil ( number 150/00 ) . routinely processed paraffin sections from 50 oral lymphomas were selected from the files of the oral pathology service at the university of sao paulo , brazil . oral lymphomas were classified according to the world health organization classification/200110 and colomo , et al.4 by morphology , immunophenotype , epstein barr virus detection and igh gene rearrangement . representative samples were diffuse large b - cell lymphoma ( dlbcl , n=17 ) ; plasmablastic lymphoma of the oral mucosa type ( pblomt , n=11 ) ; burkitt lymphoma ( bl , n=15 ) ; extranodal marginal zone b - cell lymphoma of mucosa- associated lymphoid tissue ( malt lymphoma , n=2 ) ; mantle cell lymphoma ( mcl , n=1 ) ; extranodal nk / t - cell lymphoma , nasal type ( etcl , n=3 ) , and peripheral t - cell lymphoma , unspecified ( ptcl , n=1 ) . all cases were primary of the oral cavity , since physical exam did not demonstrate signals of disease in other regions of the body . fdcs were characterized with the antibodies anti - cd21 , anti - cd35 , and anti - caldesmon . since caldesmon is also expressed in the vessel walls , consecutive sections were also stained with anti - cd34 and both stain were submitted to quantification with the use of a computerized system ( imagelab software , lido , fousp , brazil ) . five fields of each section were selected in a light microscope ( laborlux ; leitz , wetzlar , germany ) at 100x magnification . images were transferred to a computer monitor with area of 640 x 480 pixels , and the quantification was performed by subtraction of images . the values of the caldesmon+/fdcs were obtained through the total of caldesmon+/ immunoexpression minus cd34+/immunoexpression and expressed in m . since langerhans cells also express s100 protein , antibody anti - cd1a was also used in consecutive sections to exclude the langerhans cells . s100+/idcs were counted in the light microscope ( laborlux ; leitz , 400x magnification ) . ten fields were selected for each case using an integration reticule and values expressed in mm . the statistical analysis was considered only in the dlbcl , pblomt and bl , because the sample of these cases was sufficient to statistical analysis . this analysis was performed with mann - whitney test and significance statistical was evaluated at 0.05 level . a universal automatic system of staining ( dako auto staining , dako corporation , carpinteria , ca , usa ) was used for immunohistochemistry reactions with the strepatavidin - biotin standard protocol in 3-m - thick sections . the primary antibodies used were : cd21 ( dako , clone 1f8 , 1:50 , incubation for 40 min at 37c ) , cd35 ( dako , clone ber - mac - cdr , 1:20 , incubation for 40 min at 37c ) , caldesmon ( novocastra , clone td107 , 1:50 , incubation for 30 min at 37c ) , cd1a ( serotec , clone 010 , incubation for 30 min at 37c ) , s100 protein ( dako , clone z0311 , incubation for 30 min at 37c ) , and cd34 ( novocastra , clone qbend/10 , 1:50 , incubation for 30 min at 37c ) . the sections were submitted to antigen retrieval . sections for the reactions with cd21 and cd35 were immersed in target retrieval solution ph 6.0 ( dako , s1700 ) heated to 95c for 30 min . to caldesmon , cd1a , and cd34 , louis , mo , usa ) buffer 0.01 m , ph 6.0 and heated to 95c for 30 min . routinely processed paraffin sections from 50 oral lymphomas were selected from the files of the oral pathology service at the university of sao paulo , brazil . oral lymphomas were classified according to the world health organization classification/200110 and colomo , et al.4 by morphology , immunophenotype , epstein barr virus detection and igh gene rearrangement . representative samples were diffuse large b - cell lymphoma ( dlbcl , n=17 ) ; plasmablastic lymphoma of the oral mucosa type ( pblomt , n=11 ) ; burkitt lymphoma ( bl , n=15 ) ; extranodal marginal zone b - cell lymphoma of mucosa- associated lymphoid tissue ( malt lymphoma , n=2 ) ; mantle cell lymphoma ( mcl , n=1 ) ; extranodal nk / t - cell lymphoma , nasal type ( etcl , n=3 ) , and peripheral t - cell lymphoma , unspecified ( ptcl , n=1 ) . all cases were primary of the oral cavity , since physical exam did not demonstrate signals of disease in other regions of the body . fdcs were characterized with the antibodies anti - cd21 , anti - cd35 , and anti - caldesmon . since caldesmon is also expressed in the vessel walls , consecutive sections were also stained with anti - cd34 and both stain were submitted to quantification with the use of a computerized system ( imagelab software , lido , fousp , brazil ) . five fields of each section were selected in a light microscope ( laborlux ; leitz , wetzlar , germany ) at 100x magnification . images were transferred to a computer monitor with area of 640 x 480 pixels , and the quantification was performed by subtraction of images . the values of the caldesmon+/fdcs were obtained through the total of caldesmon+/ immunoexpression minus cd34+/immunoexpression and expressed in m . since langerhans cells also express s100 protein , antibody anti - cd1a was also used in consecutive sections to exclude the langerhans cells . s100+/idcs were counted in the light microscope ( laborlux ; leitz , 400x magnification ) . ten fields were selected for each case using an integration reticule and values expressed in mm . the statistical analysis was considered only in the dlbcl , pblomt and bl , because the sample of these cases was sufficient to statistical analysis . this analysis was performed with mann - whitney test and significance statistical was evaluated at 0.05 level . a universal automatic system of staining ( dako auto staining , dako corporation , carpinteria , ca , usa ) was used for immunohistochemistry reactions with the strepatavidin - biotin standard protocol in 3-m - thick sections . the primary antibodies used were : cd21 ( dako , clone 1f8 , 1:50 , incubation for 40 min at 37c ) , cd35 ( dako , clone ber - mac - cdr , 1:20 , incubation for 40 min at 37c ) , caldesmon ( novocastra , clone td107 , 1:50 , incubation for 30 min at 37c ) , cd1a ( serotec , clone 010 , incubation for 30 min at 37c ) , s100 protein ( dako , clone z0311 , incubation for 30 min at 37c ) , and cd34 ( novocastra , clone qbend/10 , 1:50 , incubation for 30 min at 37c ) . the sections were submitted to antigen retrieval . sections for the reactions with cd21 and cd35 were immersed in target retrieval solution ph 6.0 ( dako , s1700 ) heated to 95c for 30 min . to caldesmon , cd1a , and cd34 , louis , mo , usa ) buffer 0.01 m , ph 6.0 and heated to 95c for 30 min . cd35 positively stained fdcs in four cases of oral lymphomas : ( a ) two cases of dlbcl , ( b ) one malt lymphoma , and ( c ) on the case of mcl . in the dlbcl , immunoexpression was observed in pseudofollicular proliferation centers14,17 . malt lymphoma presented fdcs as a dense and confluent meshwork corresponding to colonized follicles ( figures 1c and 1d ) . mcl presented the distribution of fdcs as a loosely arranged , ill - defined and expanded meshwork ( figures 1e and 1f ) . caldesmon+/fdcs were present in all oral lymphomas and appeared as a dense and confluent meshwork ( lacy pattern ) among the neoplastic lymphoid cells ( figure 1 g ) . in cases immunopositive to cd21 and cd35 , caldesmon+/ fdcs were coincident with cd21 and cd35 stain . s100+/idcs were large cells , disclosing a round nucleus and irregular cytoplasm ( figure 1h ) . mean values and standard deviation of the quantification of caldesmon+/fdcs and s100+/idcs are presented in table 1 . there is not statistical difference of the caldesmon+/fdcs and s100+/idcs quantification between bl and pblomt , and dlbcl and pblomt , respectively . more frequently fdcs are evaluated in reactive follicles and follicular lymphomas because of microenvironmental similarity between reactive follicles and follicular lymphomas1,3,7,15,24 . oral lymphomas are almost exclusively b - cell neoplasm , presenting a diffuse pattern of growth10 . therefore , the finding of rare cd21+/cd35+/ fdcs is expected . using antibodies anti - cd21 and anti- cd35 , fdcs were visualized in two cases of dlbcl as a sparse and disrupted meshwork in neoplastic pseudofollicular proliferation centers , as demonstrated by maeda , et al.14 and mori , et al.17 that evaluated fdcs in b- cell neoplasm with a diffuse pattern . actually , the role of fdcs is to present antigens to b - cell9,21 . in the process of the antigen - presenting , the activation of complement receptors c3d ( detected by cd21 ) and c3b ( detected by cd35 ) takes place in the fdcs19 . therefore , the detection of fdcs by cd21 and cd35 depends on their activation , which occurs in reactive follicles , neoplastic pseudofollicular proliferation centers or in neoplastic follicles of follicular lymphomas14,17,19 . morphologically , malt lymphomas present reactive follicles10 . in the present study , cd21 and cd35 identified fdcs in the case of malt lymphoma that exhibited reactive follicles . bagdi , et al.1 also verified that stain for cd21 , cd23 and cd35 revealed dense fdcs meshwork in reactive follicles of seven cases of primary salivary gland or gastric malt lymphomas . in the present study , so , in malt lymphoma the immunolocalization of the fdcs by cd21 and cd35 is also dependent on the microenvironment organized by neoplastic or non - neoplastic lymphoid cells in the reactive follicles . mcl typically present a loosely arranged , ill - defined and expanded meshwork of fdcs at the periphery of the neoplasm in nodular or diffuse pattern as demonstrated in the studies of bagdi , et al.1 and mori , et al.17 . this finding is important since this pattern of distribution of fdcs resembles that of the mantle zone of non - neoplastic lymphoid follicles . also , the immunohistochemistry of fdcs in mcl is helpful to diagnosis of this disease1,17 . in t - cell and nk - cell neoplasm , the cd21+/cd35+/ fdcs are not frequently identified , as in our study1,15,24 . however , angioimmunoblastic t - cell lymphoma presented a expanded meshwork of cd21+/cd23+/cd35+/fdcs . it has been suggested that these cells may be not real fdcs , but rather fibroblastic reticular cells showing overexpression of cd21 , cd23 and cd351013 . tsunoda , et al.24 used caldesmon to evaluate neoplastic follicles of follicular lymphoma and verified a difference in fdcs immunoexpression in follicular lymphomas grade i , ii and iii . caldesmon stained fdcs in all the studied oral lymphomas , and fdcs were visualized as a lacy pattern meshwork among neoplastic lymphocytes . thus , in the b - cell neoplasms ( dlbcl , pblomt , bl , malt lymphoma and mcl ) evaluated , caldesmon+/fdcs might represent nonactive fdcs , since active fdcs are immunoexpressed in follicular microenvironment1,9,21 . in the t - cell and nk - cell neoplasms ( etcl and ptcl ) evaluated , caldesmon+/fdcs also may represent non - active fdcs or fibroblastic reticular cells with an overexpression of caldesmon . tsunoda , et al.24 suggested that caldesmon on actin filaments , and extracellular matrix adhesion receptors on fdcs may be the main way whereby fdcs twine around extracellular fibers , contributing to the formation and maintenance of the meshwork structure . in accordance to tsunoda , et al.24 , may be that in oral b - cell , t - cell and nk - cell neoplasms caldesmon is also the major way of the formation and maintenance of the meshwork structure of fdcs or fibroblastic reticular cells overexpressing caldesmon . idcs were identified by the immunoexpression of s100 protein8,9,22 . in order to exclude the possibility of langerhans cells , reactions to cd1a thus , it can be asserted that in the present study the cells positive to s100 protein were idcs , as shinzato , et al.20 and fonseca , et al.5 showed . as idcs are known as antigen - presenting cells to t - cells , they probably represent active cells in oral lymphomas , since a few non - neoplastic t - cells are always present in all b - cell neoplasm . another possibility is that idcs represent a casual feature in lymphomas due to a favorable microenvironment as also seen is non - neoplastic lymphoid tissue9,19 . thus , this study represents the first one to perform a quantitative analysis of the dcs in lymphomas . caldesmon and s100 protein were quantitatively analyzed because the immunoexpression was consistently present in all cases . it was observed that bl presented a lower statistically significant number of caldesmon+/fdcs and s100+/idcs than dlbcl . this finding may be related to the fact that bl is a specific entity and presents a high proliferation rate , shown by the high mitotic counting , spontaneous cell death , and high counting ( close to a 100% ) of ki-67 positive cells10 . also , pblomt represent a subgroup of dlbcl that is more frequent in hiv - patients4,10 . meug - moraw , et al.16 evaluated reactive bone marrow biopsies and observed that hiv - patients did not present differences in fdcs immunoexpression . therefore , cell proliferation in oral lymphomas may be related to the appropriated microenvironment to development of dcs . the microenvironment determined by neoplastic lymphoid cells in oral lymphomas is responsible by the development and expression of dendritic cells types .
objective : follicular dendritic cells ( fdcs ) and interdigitating dendritic cells ( idcs ) are dendritic cells found in lymphoid follicles , reactive follicles and in lymphomas . 
 the goal of this study was to evaluate the presence and distribution of fdcs and idcs in oral lymphomas.material and methods : immunohistochemistry reactions were applied to 50 oral lymphomas using the antibodies anti - cd21 , anti - cd35 and anti - caldesmon to fdcs , and anti - s100 protein to idcs . 
 caldesmon+/fdcs and s100+/idcs were quantified in imagelab software.results:fdcs revealed by cd21 and cd35 were positively stained in two cases of diffuse large b - cell lymphoma , one malt lymphoma , and in one case of mantle cell lymphoma . 
 fdcs were immunopositive to caldesmon in all cases , as well as idcs to s100 protein . 
 burkitt lymphoma presented a lower amount of caldesmon+/fdcs and s100+/idcs than diffuse large b - cell lymphoma and plasmablastic lymphoma of the oral mucosa type.conclusions:the microenvironment determined by neoplastic lymphoid cells in oral lymphomas is responsible by the development and expression of dendritic cells types .