Insulin as a target antigen in autoimmune diabetes: a natural repertoire as the source of antibody response

Autoimmunization to epidermal growth factor, a component of the immunological homunculus

Epidermal growth factor (EGF) is being tried as a vaccine in cancer immunotherapy with the aim of inducing neutralizing antibodies that might affect EGF-dependent tumors. Here we summarize our experience using the EGF self-molecule as an autoimmunigen. We report here that IgG anti-EGF antibodies are prevalent in healthy people and that augmentation of the response to EGF requires conjugation to an effective carrier and an adjuvant. Paradoxically, the response to EGF immunization could be enhanced by an 'immunosuppressive' treatment with cyclophosphamide, most probably by suppressing active control mechanisms. EGF is expressed in the thymus. Thus, EGF may be added to the immunological homunculus, the class of self-antigens to which there is both natural autoimmunity and natural regulation of the autoimmunity. The results using EGF as a vaccine can teach us about the homunculus and how to activate it.

A novel technique for the fluorometric assessment of T lymphocyte antigen specific lysis

The 51Cr release assay has traditionally been used to investigate effector cell cytotoxic function against labeled targets, but this method has inherent problems that include hazards associated with radioactivity, cell labeling and high spontaneous release. Here we describe a novel flow cytometric assay which addresses and improves upon the problems currently encountered with the 51Cr release assay. The fluorometric assessment of T lymphocyte antigen specific lysis (FATAL) assay employs dual staining (PKH-26 and CFSE) to identify and evaluate the target population. We found that the PKH-26/CFSE combination efficiently labeled target cells. Evaluation of the spontaneous leakage from dye labeled target cells was forty fold lower than the spontaneous leakage seen with the 51Cr release assay. The FATAL assay permitted a more accurate assessment of the effector: target ratio, and detected low levels of cytotoxic T lymphocyte (CTL) mediated lysis. There was a strong correlation between the 51Cr release and FATAL assays, when performed in parallel with identical effector and target cells (r(2)=0.998, P=<0.0001). This novel method of detecting cytolysis represents a qualitative and quantitative improvement over standard 51Cr release analysis. The FATAL assay will be of value to further investigate mechanisms of cytolysis by effector cell populations.

Oral administration of insulin to neonates suppresses spontaneous and cyclophosphamide induced diabetes in the NOD mouse

Oral administration of autoantigens to adult mice is an effective means of suppressing experimental autoimmune diseases including diabetes and experimental allergic encephalomyelitis (EAE). Different mechanisms are involved in induction of oral tolerance including active suppression, anergy and deletion. Oral tolerance is generally not inducible in the neonatal period and we previously found that EAE development in Lewis rats is enhanced when animals are fed myelin antigens as neonates. Here we report the unexpected finding that oral administration of either human insulin or the insulin B-chain peptide (10-24) in the neonatal period suppresses the development of diabetes in the non-obese diabetic (NOD) mouse. Furthermore, suppression of diabetes by neonatal oral human insulin was more effective than oral human insulin given to NOD mice (3-4 weeks of age). No protection against EAE was observed in NOD mice neonatally fed PLP (48-70) or MOG (35-55) peptide prior to EAE induction, whereas adult NOD mice orally tolerized to these peptides were protected against EAE. Neonatal administration of insulin B-chain peptide also suppressed cyclophosphamide induced diabetes in the NOD whereas oral insulin administration to 4-week-old NOD mice had no effect, suggesting that the mechanism of disease suppression in the neonate involved anergy or deletion. Our findings that neonatal feeding of human insulin or insulin B-chain peptide is effective in inhibiting diabetes when given to the NOD mouse may have applications in preventing diabetes in high risk human populations.