Normal ageing is associated with an increase in Th2 cells, MCP-1 (CCL1) and RANTES (CCL5), with differences in sCD40L and PDGF-AA between sexes

We have observed T helper type 2 (Th2) polarization of systemic immunity in patients with metastatic malignant melanoma. We hypothesized that similar changes in systemic immunity occur with ageing and may be permissive for the development of melanoma. We analysed the peripheral blood of 389 healthy blood donors. All subjects were profiled for peripheral blood T cell and B cell subsets, and 58 of these subjects were profiled for antigen-specific cytotoxic T cell subsets [cytomegalovirus (CMV), influenza and melanoma antigen recognized by T cells 1 (MART-1)]. Ninety-five separate healthy subjects underwent profiling of 42 plasma cytokines. Ageing was associated positively with CD4(+) CD294(+) Th2 cells, and associated negatively with CD3(+) T cells, cytotoxic T cells and T helper cells. Ageing was also associated negatively with CMV-, influenza- and MART-1-specific naive and CD8(+) T cells. There were significant increases in plasma monocyte chemotactic protein 1 (MCP-1) (CCL1) and regulated upon activation normal T cell expressed and secreted (RANTES) (CCL5) with age. We observed differences in cytokine profiles between males and females; specifically, women had higher levels of sCD40L and PDGF-AA. In summary, we demonstrated in healthy blood donors that ageing was associated with an increase in cellular Th2 bias and a decline in total numbers of T cells. Additionally, there was an increase in MCP-1 and RANTES with ageing. Women had higher levels of sCD40L and PDGF-AA than men.

A reproducible method for the enumeration of functional (cytokine producing) versus non-functional peptide-specific cytotoxic T lymphocytes in human peripheral blood

One of the most difficult laboratory challenges in the field of therapeutic cancer vaccines has been the development of uncomplicated/reproducible methods for the quantification of vaccine immunization efficacy in peripheral blood of cancer patients. Existing methods are limited by lack of functional information (tetramers), difficulties with standardization/reproducibility [enzyme-linked immunosorbent spot (ELISPOT)] and reliance on endogenous (sample-specific) antigen presentation (cytokine flow cytometry). Herein we present a reproducible method utilizing an artificial antigen-presenting cell platform for flow cytometry-based quantification of the frequency and activation status of peptide-specific cytotoxic T lymphocytes. The methodology [currently presented for cytomegalovirus human leucocyte antigen (HLA)-A2 cognant peptide antigens] allows simultaneous ex vivo quantification of activated (cytokine-producing) and inactive tetramer-positive T cells following HLA class I/peptide/CD28 stimulation independent of endogenous antigen presentation. The simplicity and reliability of the assay provide for high-throughput applications and automation. The utility and application of this method are discussed.

Identification of mimotopes for the H4 minor histocompatibility antigen

The H4 minor histocompatibility antigen (HA) of mice includes a single immunogenic peptide presented by H-2Kb molecules that stimulates skin allograft rejection and is immunodominant in the stimulation of cytolytic T lymphocytes (CTL) specific for multiple minor HA. We have identified H4 mimotopes that are recognized by the H4-specific M9 CTL clone through the use of a random peptide library comprised of bacterial clones expressing an inducible fusion protein tailed with the octamer sequence SXIXFXXL. Eight discrete mimotopes were identified that sensitized RMA-S cells for lysis by M9 CTL down to concentrations of 10(-11) M. Comparable reactivity was observed with a short-term, H4-specific CTL line indicating that the mimotopes were not solely specific for the selecting M9 clone. All mimotopes included Gly at p2 and either Val or Ile at p4, suggesting a requirement for a hydrophobic residue with specific conformation. All mimotopes included either Arg or His at p7, implicating a requirement for a specific positively charged amino acid at that position. The sixth position was more variable with four of eight mimotopes having a Val residue with single mimotopes including alternative amino acids, the majority of which were hydrophobic. Analysis of mimotopes for hydrophobicity and charge by reverse-phase HPLC and capillary electrophoresis respectively indicated that (i) mimotopes with Val at both p4 and p6 were hydrophobically similar (but not identical) to the natural H4 peptide, and (ii) a S --> E substitution at p1 resulted in a peptide (EGIVFVRL) with charge characteristics equivalent to those of the natural H4 peptide.

Immunodominant minor histocompatibility antigen peptides recognized by cytolytic T lymphocytes primed by indirect presentation

BACKGROUND

Indirect presentation of minor histocompatibility antigens (HA) as revealed by cross-priming of H2 heterozygous recipients effectively primes minor HA-specific cytolytic T lymphocytes (CTLs). However, it is not known if indirect priming generates CTLs specific for the same set of immunodominant minor HA recognized by CTLs primed by direct spleen cell injections.

METHODS

In order to indirectly prime minor HA-specific CTLs, we implanted (C57BL/6 x B6.C-H2d)F1 recipients with BALB.B and BALB/c splenocytes loaded into immunoisolation devices that effectively preclude direct donor:host contact. Responder spleen cells from these recipients were stimulated in vitro to expand BALB.B- and BALB/c-specific CTLs to reveal classical cross-priming.

RESULTS

Tests of CTL specificity using (1) CXB recombinant inbred strain targets that express different arrays of BALB/c minor HA and (2) high-performance liquid chromatography fractions of peptides from BALB.B Kb and Db molecules revealed that anti-BALB.B CTLs were specific for two previously identified dominant peptides, CTT-2 and CTT-5, presented by Kb molecules. Variation of responders and priming cells resulted in CTL responses to additional dominant peptides that had been identified previously with CTLs generated by direct priming with spleen cell injections. Indirect priming was not limited to this set of peptides recognized by CTLs in vitro because devices loaded with cells devoid of the CTL-detected peptides primed for accelerated skin allograft rejection.

CONCLUSIONS

Indirect presentation of minor HA in vivo stimulates the generation of CTLs specific for a subset of dominant minor HA peptides recognized by CTLs primed by direct presentation.

Immunodominant minor histocompatibility antigen peptides presented by H2Db molecules

BACKGROUND

C57BL/6 (B6) mice generate cytolytic T lymphocytes (CTLs) to a limited number of immunodominant cytotoxic T cell target (CTT) antigens and associated peptides when primed with H2-matched BALB.B spleen cells, despite multiple minor histocompatibility antigen (HA) differences. We previously showed that these CTLs recognize four Kb-bound minor HA peptides derived from CTT antigens. Here, we describe the identification of Db-bound minor HA peptides recognized by B6 anti-BALB.B CTLs.

METHODS

Peptides were extracted from Db molecules immunoprecipitated from lysates of T lymphoblasts from BALB.B mice and mice from the CXB recombinant inbred strains that express H2b and segregate minor HA from BALB/c and B6. Peptides were separated by reverse-phase high-performance liquid chromatography and tested for sensitization of targets for lysis by CTLs specific for BALB.B and the CXB strains.

RESULTS

B6 anti-BALB.B CTLs recognized a single Db-bound peptide whose distribution in CXB strains matched that of the previously reported CTT-1 minor HA. An additional Db-bound peptide (CTT-7) was recognized by B6 anti-CXBG CTLs. CTT-1 was expressed by independently derived inbred mouse strains that express H2b. CTT-1 was recognized by B6 CTLs specific for these inbred strains, except for the LP and 129 strains that stimulated CTL specific for the CTT-8 peptide expressed by these two strains.

CONCLUSIONS

These results demonstrate that B6 CTLs primed and boosted with multiple minor HA recognize a maximum of two minor HA peptides regardless of the strain of origin of H2b-matched stimulating lymphoid cells.

Brain-infiltrating cytolytic T lymphocytes specific for Theiler's virus recognize H2Db molecules complexed with a viral VP2 peptide lacking a consensus anchor residue

Mice expressing the H2b haplotype are resistant to infection with Theiler's murine encephalomyelitis virus (TMEV), which causes chronic demyelination in susceptible mice. The prominent cytolytic T-lymphocyte (CTL) response to the VP2 antigen encoded by TMEV led us to the identification of a class I-binding peptide derived from the VP2 antigen. Escherichia coli transformants overexpressing a series of 11 overlapping VP2 protein fragments were subjected to lysis and alkali digestion, and the resultant peptide pools were tested for their abilities to sensitize RMA-S targets for lysis by CTLs. The source of effector CD8+ T cells for the assays was either freshly harvested central nervous system-infiltrating lymphocytes (CNS-IL) or CNS-IL-derived VP2-specific CTL clones and lines. A 10-residue peptide at VP2 positions 121 to 130 (VP2(121-130)) (FHAGSLLVFM) was identified that sensitized targets for lysis and formed stable complexes with H2Db class I molecules. The VP2(121-130) peptide sensitized target cells for lysis by freshly harvested CNS-IL CTLs at femtomolar concentrations. Despite its relative high level of biological activity, the VP2(121-130) peptide is distinguished from other Db-binding peptides by its lack of an asparagine residue at position five, which had been previously proposed to be a requirement for Db-peptide complexing.

Reduced diversity of CTLs specific for multiple minor histocompatibility antigens relative to allograft rejection in vivo

Minor histocompatibility (H) antigens stimulate in vivo rejection of allografts compatible for the MHC and are recognized by CTLs in short term in vitro assays. CTLs generated by the in vivo priming and in vitro boosting of mice with spleen cells incompatible for multiple minor H Ags are specific for a limited number of dominant Ags (peptides). We have addressed the issue of the identity of the Ags that stimulate rejection of solid tissue allografts vs the H Ags recognized by CTLs. C57BL/6 recipients reject skin grafts from BALB.B and CXB recombinant inbred strains with no significant differences in survival times. Primary grafts from these same strains prime for accelerated rejection of second-set grafts from all CXB strains regardless of inheritance of dominant Ags detected by CTLs. However, CTLs primed by these allografts and boosted in vitro do not exhibit ranges of reactivity with lymphoblast targets from CXB strains predicted by in vivo rejection, suggesting that CTLs primed by multiple Ag-incompatible skin grafts do not recognize all H Ags that stimulate allograft rejection. The fact that first- and second-set BALB.B skin grafts prime for accelerated rejection of 11/13 congenic strains defining single BALB/c minor H Ags indicates that multiple H Ags stimulate allograft rejection. However, CTLs from C57BL/6 mice primed with BALB.B grafts and boosted with BALB.B spleen cells recognize only the H4 Ag from this panel of congenic strains. Limited diversity of the CTL response is corroborated by the recognition of three minor H peptides (including H4 as the most prominent) eluted from Kb molecules from a BALB.B tumor by these CTLs. These results indicate that CTLs recognize only a limited number of Ags operative in vivo and do not accurately reveal the complexity of the antigenic specificity of the in vivo response.

Reduced diversity of CTLs specific for multiple minor histocompatibility antigens relative to allograft rejection in vivo

Minor histocompatibility (H) antigens stimulate in vivo rejection of allografts compatible for the MHC and are recognized by CTLs in short term in vitro assays. CTLs generated by the in vivo priming and in vitro boosting of mice with spleen cells incompatible for multiple minor H Ags are specific for a limited number of dominant Ags (peptides). We have addressed the issue of the identity of the Ags that stimulate rejection of solid tissue allografts vs the H Ags recognized by CTLs. C57BL/6 recipients reject skin grafts from BALB.B and CXB recombinant inbred strains with no significant differences in survival times. Primary grafts from these same strains prime for accelerated rejection of second-set grafts from all CXB strains regardless of inheritance of dominant Ags detected by CTLs. However, CTLs primed by these allografts and boosted in vitro do not exhibit ranges of reactivity with lymphoblast targets from CXB strains predicted by in vivo rejection, suggesting that CTLs primed by multiple Ag-incompatible skin grafts do not recognize all H Ags that stimulate allograft rejection. The fact that first- and second-set BALB.B skin grafts prime for accelerated rejection of 11/13 congenic strains defining single BALB/c minor H Ags indicates that multiple H Ags stimulate allograft rejection. However, CTLs from C57BL/6 mice primed with BALB.B grafts and boosted with BALB.B spleen cells recognize only the H4 Ag from this panel of congenic strains. Limited diversity of the CTL response is corroborated by the recognition of three minor H peptides (including H4 as the most prominent) eluted from Kb molecules from a BALB.B tumor by these CTLs. These results indicate that CTLs recognize only a limited number of Ags operative in vivo and do not accurately reveal the complexity of the antigenic specificity of the in vivo response.

The preferential cytolytic T lymphocyte response to immunodominant minor histocompatibility antigen peptides

C57BL/6 mice preferentially generate cytolytic T lymphocytes (CTL) to a limited number of immunodominant minor antigens and associated immunogenic peptides when primed with H2-matched Balb.B spleen cells despite multiple minor histocompatibility (H) antigen differences. We have examined the complexity of dominant H antigens recognized by these CTLs to estimate the number of peptides associated with single antigens. Peptides eluted from Kb molecules of lymphoblasts from Balb.B and CXB recombinant inbred (RI) strains were tested for sensitization of RMA-S cells for lysis by short-term C57BL/6 CTL lines specific for Balb.B and CXB strains. Anti-Balb.B CTLs recognized four Kb-bound peptides; subsets of these peptides were recognized by anti-CXB CTLs when tested with peptides from the respective CXB strains. Single peptides segregated independently among the CXB strains, confirming that single peptides were encoded by independently segregating alleles. These peptides were expressed in diverse inbred mouse strains and were recognized preferentially by C57BL/6 CTLs stimulated by different inbred mouse strains. This set of peptides was subclassified by their capacity to sensitize targets when presented in unfractionated mixtures of Kb-bound peptides. The peptide associated with the previously classified dominant CTT-2 antigen was the only peptide to strongly sensitize RMA-S cells for lysis under these conditions. These results suggest that dominant peptides have a wide strain distribution and may have a distinct advantage over dominated peptides in binding to class I molecules and/or in presentation to CTLs.