Working Model for Immune Cell Expression TLRs function as critical sensors of microbes, and pathogenic antigens of non-self, or self origins.  TLR signaling, which initiates an immune response  occurs through major pathway nodes such as NF-kB and IRF circuits. These result in a pro-inflammatory cytokine cascade which directs the immune response. Differential TLR expression on cells can be useful in identification of distinct cell subsets, activation states and/or functional roles of cells which bear them. TLR phenotyping in combination with cell lineage marker (CD) phenotyping may provide an important approach for immune cell analysis. A prime application of TLR phenotyping is in the analysis of  Dendritic cells (DCs) which are potent activators of the immune response through their key role as antigen presenting cells (APCs) Dendritic cell subsets appear to express different sets of TLRs.  Human plasmacytoid dendritic cells express TLR7 and TLR9 while human myeloid dendritic cells express TLR1, TLR2, TLR3, TLR5, TLR6 and TLR8 thus providing a means to utilize TLRs to identify different DC subsets.   A variety of reports have demonstrated that for most TLRs, mRNA is expressed in T or B lymphocytes.  However, functional expression of individual or sets of TLRs in specific subsets of T or B cells also appears to be selective.  An example is that TLR8 is expressed in CD25+CD4+ Tregs but not in naïve T cells which are CD25-/CD4+. TLR5 is expressed in both CD25+CD4+Tregs and naïve T cells. TLR1 and TLR9 are expressed in B cells but expression is biased  toward CD19+/CD5+ B cells. An overall and systematic categorization of TLR expression patterns still remains to compiled and TLR phenotyping should be important Plasmacytoid Dendritic Cells (pDCs) identified as CD14-/CD123+/TLR9+ cells in monocyte gate. for understanding the connection between the TLR presence and signaling pathways of different cell subsets.  To address this IMGENEX has developed a working model from information gleaned for the literature (Table1). The majority of the TLR expression shown in Table 1 is based on ligand responses. Availability of specific TLR-conjugated antibody probes should provide an approach for improved analysis. IMGENEX provides an expanding number of fluorescently labeled TLR antibodies and kits for TLR Phenotyping and subset analysis .  Examples are shown below.   TLR Phenotyping by Flow Cytometry  Specificity  Cat. No.  Species Reactivity FITC    PE   Alexa Fluor  488   Alexa Fluor 647   TLR1  IMG-5012  Human, Mouse, Rat • •   TLR2  IMG-416  Dog, Human • • • •  IMG-6320  Human, Mouse •         TLR3    DDX0470  Human, Mouse     • •  DDX0474  Human, Mouse, Rat     • •  IMG-315  Dog, Human • •       TLR4  IMG-417  Dog, Human • • • •  IMG-428  Mouse • •  IMG-5031  Human, Mouse, Rat • • • •   TLR5  IMG-663  Dog, Human, Mouse • •      IMG-664  Dog, Human, Mouse • • • •   TLR6  IMG-304  Human • • • •   TLR7  IMG-581  Human, Mouse •        IMG-665  Human, Mouse • •       TLR8  DDX0480  Human   • • •  DDX0482  Human, Mouse     •    IMG-321  Human, Mouse • • • •   TLR9  IMG-305  Human, Mouse, Rat • • • •   TLR10  IMG-386  Human • • TLR Ligands   Specificity  Ligand Cat. No.   Pam3CSK4  TLR1 and TLR2 IMG-2201   Poly(I).PolyC  TLR3 IMG-2203   LPS from E. Coli  TLR4 IMG-2204   Flagellin, Recombinant  TLR5 IMG-2205   MALP-2  TLR6/TLR2 IMG-2206   Imiquimod  TLR7 IMG-2207   Imidazoquinoline Resiquimod (R-848)   TLR8 IMG-2208   CpG ODN (1668) with negative control oligo  TLR9 (Mouse) IMG-2209M   CpG ODN (2006) plus negative control oligo  TLR9 (Human) IMG-2209H Inhibitory Peptides  Description Cat. No.  IKKg NEMO Binding Domain IMG-2000  NF-kB p65 (Ser276) IMG-2001  NF-kB p65 (Ser529/536) IMG-2003  NF-kB p50 IMG-2004  MyD88 IMG-2005  TIRAP IMG-2006