SummaryThe human cell line T2 has been reported to be class I assembly deficient, and accordingly expresses reduced amounts of HLA-A2 and no HLA-B5 at the cell surface. By immunoblotting we observe the steady-state class I heavy chain levels of T2 to be near normal when compared with the identical class I alleles of the wild-type cell line T1. In pulse chase experiments, formation of heavy chain/3z-microglobulin complexes is observed for both HLA-A2 and HLA-B5. Culture at reduced temperatures (26 or 20~ does not increase the amount of class I molecules transported, unlike what has been reported for the class I assembly-deficient mouse mutant cell line RMA-S. The HLA-B5 and the HLA-A2 complexes formed by T2 are thermolabile in cell lysates, albeit to different degrees. The thermolability of HLA-B5 can be overcome by addition of HLA-B5-presentable peptides, obtained by trifluoroacetic acid extraction from an HLA-B5-positive cell line, underlining the necessity of peptide for class I stability and indicating that T2-derived class I complexes are devoid of peptide. Cytoplast fusion of T2 cells with RMA-S cells shows the defect in class I assembly of RMA-S to be similar to that of T2. Localization of class I molecules observed by immuno-electron microscopy reveals the accumulation in the T2 cell line of both HLA-B5 and HLA-A2 in the endoplasmic reticulum (ER). Class I molecules are present in all the cisternae of the Golgi complex of T2, but the ratio of HLA-A and -B locus products in the Golgi area differs significantly from that at the cell surface. We conclude that the requirement for peptide in transport of class I molecules manifests itself at a stage beyond the ER, most likely the Golgi area.

Mice harboring a deletion of the gene encoding the transporter associated with antigen presentation-1 (TAP1) are impaired in providing major histocompatibility complex (MHC) class I molecules with peptides of cytosolic origin and lack stable MHC class I cell surface expression. They consequently have a strongly reduced number of CD8+ T cells. To examine whether selection of CD8+ T cells is dependent on TAP- dependent peptides, we partially restored MHC class I cell surface expression in TAP1-deficient mice by introduction of human beta 2- microglobulin. We show that selection of functional CD8+ T cells can be augmented in vivo in the absence of TAP1-dependent peptides.

Clinical, microbiological, serological, histological, and therapeutic aspects of two separate outbreaks of caprine keratoconjunctivitis are described. The disease was characterized by a high rate of contagion, rapid onset, intense lacrimation, conjunctival hyperemnia, and corneal opacity with neovascularization. In addition, many of the animals developed respiratory illness during the second epidemic. The only organism consistently isolated was Mycoplasma conjunctivae. A total of 23 strains were isolated from 18 inflamed conjunctivae, one normal conjunctiva, and the nasal secretions of four goats with concomitant respiratory illness. The convalescent sera of goats in the first outbreak had neutralizing antibody titers to M. conjunctivae that ranged from 1:32 to 1:256. In the milder second outbreak the antibody titers ranged from 1:4 to 1:32 in animals with only ocular disease and from 1:4 to 1:64 in animals with only respiratory disease. Whereas little change was noted in antibody titers of goats with only localized eye disease, 43% of the goats with respiratory disease showed significant fourfold rises. The histological picture was consistent with acute corneal infection. Animals requiring antibiotic treatment appeared to respond favorably to a combination of oxytetracycline and polymyxin B, but not to penicillin. These findings suggest that M. conjunctivae is one cause of epidemic caprine keratoconjunctivitis.

The induction of caprine keratoconjunctivitis by the subconjunctival inoculation of a cloned culture of Mycoplasma conjunctivae is described. The clinical course of the experimental disease was similar to that noted in naturally occurring outbreaks of "pink-eye" among goats, and biopsies of inflamed conjunctivae showed similar histological response. M. conjunctivae was consistently recovered from the inflamed conjunctival tissues of inoculated animals that developed ocular disease, thus fulfilling Koch's postulates and establishing this organism as an etiological agent of caprine keratoconjunctivitis. Immunological studies suggested that cellular immune mechanisms may play a role in protecting animals from disease produced by this mycoplasma.