Residual public repertoires to self.

The consensus view about the constitution of the T cell receptor repertoire has shifted greatly even during this decade. Although the discovery of autoimmunity in the fifties had clearly shown that a repertoire must exist directed against self antigens, the extent of this repertoire was not fully appreciated. In our work we have tried to elucidate the nature of the antigenic specificities against which this self-directed repertoire is directed. The non-tolerized (residual) self-directed repertoire is a direct consequence of the hierarchy of antigenic determinant display, and is the most important influence in the organism's choice of which T cells to delete. Certain determinants remain "silent" and are neither displayed in the thymus nor in the periphery: these are a heterogeneous group which are invisible to T cells for a variety of reasons. One reason relates to the processing and presentation of determinants, and a second derives from the nature of the T cell receptor (TcR) and the avidity of the T cell for its target specificity.

T cell receptor complementarity determining region 3 length analysis reveals the absence of a characteristic public T cell repertoire in neonatal tolerance. The response in the "tolerant" mouse within the residual repertoire is quantitatively similar but qualitatively different.

All adult BALB/c mice immunized with hen egg white lysozyme (HEL) or its dominant determinant, peptide (p)106-116, mount a T cell response using a "public" Vbeta8.2Jbeta1.5 T cell clone. Neonatal exposure to tolerance-inducing doses of antigen can drastically diminish responsiveness in the draining lymph nodes but not in the spleens of animals challenged as adults with the cognate antigen. To determine the role of T cell deletion or anergy within the mechanisms of observed neonatal "tolerance," we treated neonatal BALB/c mice with HEL and directly followed the characteristic public clone using complementarity determining region 3 length T cell repertoire analysis. Our results confirm that despite intraperitoneal injection of neonates with a high dose of HEL emulsified in incomplete Freund's adjuvant, a strong splenic proliferative response to HEL was observed upon recall. However, the adult splenic T cell response of these neonatally treated mice lacked the usual Vbeta8.2Jbeta1.5 public clone characteristic of HEL-primed BALB/c mice. After challenge with HEL-complete Freund's adjuvant as adults, immunoglobulin (Ig)G2a isotype antibody was drastically reduced, and IgG1 was found to be the predominant anti-HEL IgG isotype expressed, indicating a deviation of cytokine response toward T helper type 2. 5-wk-old mice, nasally instilled with tolerogenic doses of HEL p106-116, also showed significant inhibition of this public T cell expansion. These results demonstrate that during neonatal and adult nasal tolerance induction, deletion/anergy removes the public clone, exposing a response of similar specificity but that is characterized by the T helper type 2 phenotype and a splenic residence.

Enhanced immunogenicity of a recombinant genital warts vaccine adjuvanted with monophosphoryl lipid A.

The regression of genital warts is believed to be a T-cell-mediated immune effect. We have sought to enhance the immunogenicity of a therapeutic vaccine for the treatment of genital warts with the use of the adjuvant monophosphoryl lipid A (MPL-immunostimulant), a detoxified form of the lipopolysaccharide (LPS) of Salmonella minnesota R595. The comparative immunogenicity and reactogenicity of a recombinant human papillomavirus type 6 (HPV6) L2E7 fusion protein in either aqueous, oil-in-water emulsions or Alhydrogel formulations containing MPL was evaluated. We conclude that the simple addition of MPL to the L2E7 fusion protein already adsorbed onto Alhydrogel preferentially enhances antigen specific in vitro T-cell proliferative responses, IFN gamma production and in vivo delayed type hypersensitivity responses without increasing its reactogenicity.

Effect of T-helper cytokine environment on specificity of T-cell responses to mycobacterial 65,000 MW heat-shock protein.

The purpose of this work was to determine if the fine specificity of T cells differed between mice immunized with an antigen in a T helper 1 (Th1) cytokine-dominated environment as compared with a T helper 2 (Th2) cytokine-dominated environment. It was found that splenic T cells from mice immunized with mycobacterial heat-shock protein (hsp 65) and interleukin-12 (IL-12) produced less interleukin-4 (IL-4) and more interferon-gamma (IFN-gamma) in response to stimulation with hsp 65 in vitro than did T cells from mice immunized with hsp 65 alone. The T-cell proliferative response to hsp 65 did not differ between the two groups of mice, although the responses were higher than those of T cells from non-immunized mice. Strikingly, T cells from mice given hsp 65 and IL-12 gave significantly higher responses to six peptides (corresponding to the sequence of hsp 65) to which T cells from mice immunized with hsp 65 alone did not respond. It is considered that different epitopes are presented to T cells (possibly owing to changes in antigen processing) if the environment is shifted, by IL-12, from Th2 towards Th1 cytokines.

CD4+ Th2 cells specific for mycobacterial 65-kilodalton heat shock protein protect against pristane-induced arthritis.

Previous studies showed that mice with pristane-induced arthritis (PIA) and those protected from the disease by preimmunization with mycobacterial 65-kDa heat shock protein (hsp65), possess raised immune responses to hsp65. Thus, a paradox exists whereby T cells from both arthritic and hsp65-protected animals proliferate vigorously in response to the same Ag. Here we demonstrate that T cells from mice with PIA and hsp65-protected mice produce different cytokines in vitro in response to hsp65. The use of a sensitive CelELISA to measure Ag-driven lymphokine production revealed that spleen cells from hsp65-protected mice, but not those from pristane-injected or normal mice, produced the Th2-associated cytokines IL-4, IL-5, and IL-10 in response to stimulation with hsp65. By contrast, the Th1-associated cytokines IL-2 and IFN-gamma were produced by spleen cells from mice of all groups in response to hsp65. Furthermore, there was a dramatic increase in the IgG1 to IgG2a ratio of anti-hsp65 Abs from arthritic to protected mice. Thus, it appears that a Th2 response is protective against PIA. To examine this theory, a regimen of IL-12 administration which polarizes the hsp65-specific (Th2) immune response toward Th1 was identified. This regime abolished hsp65-mediated protection against PIA. Other experiments revealed that the specificity of the response to hsp65 was important, as other bacterial proteins known not to protect against PIA induced similar Th2-associated cytokines in vitro. It is considered that the protection afforded by hsp65 preimmunization is mediated by Th2-associated cytokines produced by hsp65-specific CD4+ T cells.

Incorporation of cells into an ELISA system enhances antigen-driven lymphokine detection.

The ability to measure successfully the levels of Th1 or Th2 cytokines during an in vitro antigen-driven, polyclonal T-cell response has proven to be more difficult than expected. Here we describe the development of a highly sensitive cell-based ELISA (celELISA) technique for the detection of murine Th1 and Th2 cytokines. The celELISA combines the quantification aspects of the conventional sandwich ELISA with the sensitivity of the ELISPOT assay. The celELISA was particularly useful for the improved detection of IL-2, IL-4, and to a lessor extent, IFN-gamma.

T-helper 1 dominated responses to erythrocyte Band 3 in NZB mice.

Band 3, the red blood cell (RBC) anion channel protein, is the target autoantigen for the pathogenic RBC autoantibodies and T-helper (Th) cells in New Zealand Black (NZB) mice with autoimmune haemolytic anaemia (AIHA). To determine the subpopulation of these Th cells, they were stimulated with Band 3 and the profile of the cytokines elaborated by the responding cells was measured. NZB T cells stimulated with Band 3 produced high levels of the Th1 cytokine, interferon-gamma (IFN-gamma), but little or no interleukin-4 (IL-4), IL-5 or IL-10. Similar patterns were produced by NZB T cells responding to a spectrin preparation from the RBC membrane skeleton, or to mycobacterial heat-shock protein (hsp) 65 following immunization of mice with hsp 65 in incomplete adjuvant. By contrast, T cells from CBA mice similarly immunized with hsp 65 produced high levels of IL-4 and IL-5 in response to hsp 65. Examination of the isotype of the RBC-bound immunoglobulins in NZB mice revealed that immunoglobulin G2a (IgG2a) autoantibodies were the first to be detected in most mice and that later in the disease, IgG3 autoantibodies were often prominent. It is concluded that, contrary to expectation, the development of RBC autoantibodies in NZB mice is associated with Th1 cytokine-dominated responses.