Differential binding of two monoclonal antibodies directed against the chicken CD8 alpha molecule

New alleles of chicken CD8 alpha and CD3d found in Chinese native and western breeds

Chinese native chicken breeds provide useful resources for the study of genetic diversity. In this study, the alleles of CD8 alpha and CD3d cDNA from Chinese native and introduced western breeds of chicken were analyzed at the sequence level. Six alleles were found, due to 13 amino acid replacements in the extracellular domain of the CD8 alpha sequence. There were four alleles detected in the Chinese strains, and alleles 5 and 6 were identified for the first time. Allele 6 was shared by Langshan, Beijing Fatty and Recessive White Feather chickens. Allele 2, found in the Bigbone strain, was the same as that found in the Leghorn strain H.B15.H7, and allele 3 in the Xianju breed was also the same as in the Leghorn strain H.B15.H12. Two Leghorn lines (RPL line 7 and AY519197) and the Camellia possessed an allele (alleles 1, 4 and 5), respectively, that was not found in the other lines. Nine out of 13 amino acid replacements were situated in the putative major histocompatibility complex (MHC) class I binding CDR1 (positions 30, 33 and 34), CDR2 (positions 58, 62, 63 and 65) and CDR3 (positions 90 and 106). Except for the Xianju breed, the CD8 alpha cDNA of Chinese native chicken breeds shared high homology. Two alleles were found in CD3d. Three additional nucleotides were found at positions 64, 65 and 66 in the newly discovered allele 2. This led to a difference of four amino acids (at residues 22, 23, 24 and 25) in the extracellular domain of CD3d cDNA from the Gushi, Recessive White Feather and ISA chickens compared with these of the White Leghorn and T11.15 (NM_205512). Five hybridoma clones (1C9, 1H5, 4B11, 6G5 and 13C5) against chicken CD8 alpha were generated by DNA immunization. Two monoclonal antibodies (mAbs), 6G5 and 4B11, showed reactivity to the splenocytes from five Chinese native chicken breeds, the Recessive White Feather chicken and the Leghorn (AY519197), while mAbs 1C9, 1H5 and 13C5 showed no reaction with these breeds.

Gamma/delta T cell response of chickens after oral administration of attenuated and non-attenuated Salmonella typhimurium strains

Poultry represents an important source of Salmonella infection in man. Despite intensive research on immunity, little is known about the involvement of T cell sub-populations in the immunological response of chickens against infection with non-host-adapted Salmonella (S.) serovars. In this study, the T cell composition of blood lymphocytes (CD4(+)CD8(+); CD4(+)CD8(-); CD4(-)CD8(+); CD8(+)TcR1(+); CD8(-)TcR1(+), CD8(+)TcR1(-)) after oral administration of the non-attenuated S. typhimurium wild-type strain 421 (infection) or the attenuated vaccine strain Salmonella vac((R)) T (immunization) to day-old chicks was investigated and compared with non-treated chickens by flow cytofluorometry. Additionally, the occurrence of T cell sub-populations (CD4(+); CD8(+); TcR1(+)(gammadelta); TcR2(+)(alphabeta(1))) in ceca, spleen and bursa of Fabricius of the birds was studied immunohistologically. Blood samples and tissues were examined between days 1 and 12 of age. Chicks inoculated with S. typhimurium 421 or Salmonella vac((R)) T showed significantly elevated percentages of CD8(+)TcR1(+) in blood on days 7, 8 and 9, or on day 8 in comparison to control animals. The CD4 to CD8 cell ratio was about 3:1 in infected animals on day 5 of age. In the organs of treated chicks the numbers of CD8(+)(gammadelta) and TcR1(+)(gammadelta) cells had markedly increased on days 4 and 5 in ceca, 8 and 9 in the bursa and 9 and 12 in the spleen. Moreover, infected or vaccinated birds revealed larger quantities of CD4(+) and TcR2(+) T cells in ceca on days 4 and 5. As shown by double staining, the TcR1(+) cells in the organs of infected animals additionally carried the CD8 antigen. In conclusion, immunization of day-old chicks with the attenuated Salmonella live vaccine strain resulted in the same changes in T cell composition as seen after infection with the non-attenuated Salmonella wild-type strain, but at a lower level. The remarkable increase of CD8(+)TcR1(+)(gammadelta) double positive cells in treated birds indicates an important role of this cell sub-population in the immunological defense of chickens against Salmonella exposure.

Lymphocytic infiltration in the chicken trachea in response to Mycoplasma gallisepticum infection

A prominent feature of disease induced by Mycoplasma gallisepticum is a lymphoproliferative response in the respiratory tract. Although this is also seen in other mycoplasma infections, including Mycoplasma pneumoniae, the phenotype of the lymphocytes infiltrating the respiratory tract has not been determined. In this study, the numbers and distribution of lymphocytes in the tracheas of chickens infected with a virulent strain of M. gallisepticum were examined. Three groups of chickens were experimentally infected with M. gallisepticum and three unchallenged groups were used as controls. One infected and one control group were culled at 1, 2 and 3 weeks post infection. Tracheas were removed and examined for the presence and number of T cells carrying CD4, CD8, TCRgamma7, TCRalphabeta1 or TCRalphabeta2 markers. There was no significant difference in the number of CD8+ cells in the upper, middle and lower trachea. High numbers of both CD4+ and CD8+ cells were found with variable numbers of TCRalphabeta1+ and TCRalphabeta2+, but no TCRgammadelta+, cells throughout the time course. The distribution of CD4 cells was dispersed, while the CD8+ cells were clustered in follicular-like arrangements. No difference was detected in the distribution of TCRalphabeta1+ and TCRalphabeta2+ cells. The titre of mycoplasma genomes in the trachea decreased significantly from 1 to 2 weeks, while the mucosal thickness of the trachea increased significantly from 1 to 2 weeks then decreased from 2 to 3 weeks, indicating resolution of the lesions following control of infection. This study is the first to examine the phenotypes of T lymphocytes infiltrating the respiratory tract during mycoplasma infections. The findings suggest involvement of specific stimulation of CD8+ cells, particularly in the acute phase of disease.

Extrathymic CD4/CD8 double positive T cells

Mature T lymphocytes expressing the alphabeta T cell receptor are generally classified as either CD4+ or CD8+, based on the mutually exclusive expression of these two lymphocyte coreceptors. Contrary to this conventional division, there is considerable evidence that significant numbers of CD4/CD8 double positive (DP) lymphocytes exist in the peripheral blood and secondary lymphoid tissues of swine, chickens and monkeys. Although CD4/CD8 DP T cells are rarely present in human peripheral blood the relative percentage of this lymphocyte population can increase spontaneously in healthy individuals and in persons suffering from certain disease conditions. DP can also be found among those T cells infiltrating arthritic joints, rejected kidney grafts and certain tumors. In humans, and rats, CD4/CD8 DP T cells appear transiently following activation of their progenitors. Murine DP cells have been described as a subset of intraepithelial lymphocytes (IELs). However, the relationship of IELs to DP cells in the peripheral blood of other species is unknown. Because of their unconventional phenotype and rarity in human and mice, most immunologists have ignored extrathymic CD4/CD8 DP lymphocytes. Nevertheless, their abundance in the peripheral blood of swine, monkeys and chickens makes it impossible to dismiss this lymphocyte population. Here are reports that have described extrathymic lymphocytes exhibiting a CD4+CD8dim phenotype in several species reviewed. Swine and monkey lymphocytes with this phenotype are represented by small resting cells that simultaneously express CD4 and CD8alpha molecules. The available evidence favors the notion that such DP T cells in swine are comprised predominantly of MHC class II restricted memory CD4+ helper T cells that after activation have acquired the ability to express the CD8alpha chain and then to maintain this DP phenotype. Moreover, porcine CD4/CD8 DP T cells appear to be comprised of memory cells due to their ability to respond to recall antigen, resilience to thymectomy, increase in proportion with age, expression of memory T cell markers, production of interferon-gamma and localization to inflammatory sites. Some of these characteristics are also descriptive of human and monkey CD4/CD8 DP T cells. Thus, in swine, humans and monkeys, these phenotypically distinct lymphocytes appear to represent a primed T cell subset. The possible functional significance of the simultaneous expression of the CD4 and CD8 co-receptors on mature T cells is discussed.

Cross-reactive anti-chicken CD4 and CD8 monoclonal antibodies suggest polymorphism of the turkey CD8alpha molecule

To measure turkey CD4 and CD8 T cell levels, the cross-reactivity of mouse anti-chicken CD4 and CD8 monoclonal antibodies (mAb) with turkey leucocytes was tested by flow cytometric analysis of blood obtained from individuals in five turkey lines. The turkey lines used included a randombred control population (RBC2), a subline (F) of RBC2 selected for increased 16-wk BW, and a sire line (A, B, and C) from each of three commercial turkey breeders. Peripheral blood lymphocytes were isolated and stained with single or dual color staining. The CT8 mAb (anti-chicken CD8alpha) failed to detect the CD8alpha molecule in some turkeys, and there were large line differences in ability to detect the CD8alpha molecule. However, certain anti-chicken CD8alpha mAb (3-298, 3-292, and 11-39) had good cross-reactivity with the turkey CD8alpha molecule. These present data indicate that the turkey CD8alpha molecule is polymorphic. Some anti-chicken CD4 mAb (CT4, 2-6, 2-35, and 7-125) were also cross-reactive with the turkey CD4 molecule. Immunoprecipitation and Western blotting showed that the 3-298 mAb precipitated a 33- to 35-kDa polypeptide from the turkey splenocyte lysate under reducing conditions. The availability of cross-reactive anti-chicken CD4 and CD8 mAb will facilitate the studies of immune responses in turkeys.

Report on the analyses of mAb reactive with porcine CD8 for the second international swine CD workshop

Based on an analysis of their reactivity with porcine peripheral blood lymphocytes (PBL), only three of the 57 mAbs assigned to the T cell/activation marker group were grouped into cluster T9 along with the two wCD8 workshop standard mAbs 76-2-11 (CD8a) and 11/295/33 (CD8b). Their placement was verified through the use of two-color cytofluorometry which established that all three mAbs (STH101, #090; UCP1H12-2, #139; and PG164A, #051) bind exclusively to CD8+ cells. Moreover, like the CD8 standard mAbs, these three mAbs reacted with two proteins with a MW of 33 and 35 kDa from lymphocyte lysates and were, thus, given the wCD8 designation. Because the mAb STH101 inhibited the binding of mAb 76-2-11 but not of 11/295/33, it was given the wCD8a designation. The reactivity of the other two new mAbs in the T9 cluster with the various subsets of CD8+ lymphocytes were distinct from that of the other members in this cluster including the standards. Although the characteristic porcine CD8 staining pattern consisting of CD8low and CD8high cells was obtained with the mAb UCP1H12-2, a wider gap between the fluorescence intensity of the CD8low and CD8high lymphocytes was observed. In contrast, the mAb PG164A, not only exclusively reacted with CD4-/CD8high lymphocytes, but it also failed to recognize CD4/CD8 double positive lymphocytes. It was concluded that this mAb is specific for a previously unrecognized CD8 epitope, and was, thus, given the wCD8c designation. A very similar reactivity pattern to that of PG164A was observed for two other mAbs (STH106, #094; and SwNL554.1, #009). Although these two mAbs were not originally positioned in the T cell subgroup because of their reactivity and their ability to inhibit the binding of PG164A, they were given the wCD8c designation. Overall, five new wCD8 mAbs were identified. Although the molecular basis for the differences in PBL recognition by these mAbs is not yet understood, they will be important in defining the role of CD8+ lymphocyte subsets in health and disease.