Transgenic Mice Overexpressing PG1 Display Corneal Opacity and Severe Inflammation in the Eye.

Antimicrobial peptides (AMPs) are of interest as alternatives to antibiotics or immunomodulators. We generated and characterized the phenotypes of transgenic mice overexpressing protegrin 1 (PG1), a potent porcine cathelicidin. No obvious differences were observed between PG1 transgenic and wild-type mice in terms of growth, development, general behaviour, and the major immune cell population. However, PG1 transgenic mice intranasally infected with Staphylococcus aureus resulted in a reduction in microscopic pulmonary injury, improved clearance of bacteria, and lower proinflammatory cytokine secretion, compared to those of wild-type mice. On the other hand, approximately 25% of PG1 transgenic mice (n = 54/215) showed corneal opacity and developed inflammation in the eye, resulting ultimately in phthisis bulbi. Immunohistochemical analyses revealed that PG1 and its activator, neutrophil elastase, localized to the basal cells of the cornea and glands in eyelids, respectively. In addition, apoptosis indicated by a Terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL)-positive signal was detected from flat cells of the cornea. Our study suggests that the expression regulation or localization of AMPs such as PG1 is important to prevent their adverse effects. However, our results also showed that the cytotoxic effects of PG1 on cells could be tolerated in animals, except for the eyes.

Generation and evaluation of the efficacy of rhesus monkey soluble cytotoxic T lymphocyte-associated antigen-4 in the allogeneic mixed lymphocyte reaction.

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4; CD152) is a transmembrane protein that is structurally similar to CD28. As CTLA-4 has a much higher binding affinity to B7 than CD28, several approaches using soluble CTLA-4 have been tried to down-regulate T cell activity by blocking the interaction between CD28 and B7. We constructed soluble rhesus monkey CTLA-4 immunoglobulin (CTLA-4Ig) containing a critical binding site to B7 combined with a constant Ig heavy chain region in a mammalian system. Flow cytometry analyses indicated that soluble rhesus monkey CTLA-4Ig bound to rhesus monkey CD86 (B7.2). Moreover, soluble rhesus monkey CTLA-4Ig more effectively blocked the rhesus monkey-rhesus monkey allogeneic mixed lymphocyte reaction compared with that of humans. These results indicate that soluble rhesus monkey CTLA-4Ig may be useful in preclinical trials in a rhesus monkey model.

Porcine testicular extract inhibits T cell proliferation by blocking cell cycle transition from G1 phase to S phase.

Since T cells express diverse sex steroid hormone receptors, they might be a good model to evaluate the effects of sex steroid hormones on immune modulation. Porcine testicular extract contains several sex steroid hormones and may be useful to study the effects of sex steroid hormones during T cell activation. We have examined the effects of the porcine testicular extract on T cell activation: proliferation and secretion of cytokines (IL-2 and IFN-γ) by activated T cells were severely decreased after treatment with porcine testicular extract. The extract produced an immunosuppressive effect and inhibited the proliferation of activated T cells by blocking the cell cycle transition from the G(1) phase to S phase. These effects were mediated by a decrease in the expression of cyclin D1 and cyclin E and constitutive expression of p27(KIP1) after T cell activation.