Experimental uveitis in isolated humoral and cellular immunity

Immunological concepts and the eye: a review of the classical and ocular arthus reactions

Inflammatory processes can involve any tissue in the eye. Despite advances in therapy, the sequelae of inflammation continue to be a major cause of visual impairment. Knowledge of disease pathogenesis in clinical ocular inflammations remains imprecise, and defined models are crucial in developing this understanding and evolving rational approaches to treatment. This review analyzes the contributions that studies of the classical and Arthus ocular Arthus-type reactions have made as to how the eye functions as an immunological entity. The anticipated development of therapeutic agents that may modulate immune processes with remarkable specificity, gives a new impetus to such experimental studies.

An acute ocular inflammatory reaction induced by intravitreal bovine serum albumin in presensitized rabbits: the effect of phentolamine

An acute inflammatory reaction in the uvea was challenged by an intravitreal injection of bovine serum albumin (BSA) in presensitized rabbits. During the observation time of 3 h, intraocular pressure (IOP) increased, anterior uveal blood vessels were dilated, miosis was produced, and as a sign of the breakdown of the blood aqueous barrier, protein content in the aqueous humour was increased. In the contralateral eye, the reaction consisted of an increase in IOP and a disruption of the blood aqueous barrier. As an evidence of the immunological mechanism of this acute reaction, presensitized animals intravitreally injected with saline or unimmunized rabbits which were injected with BSA showed no significant changes in IOP, pupillary diameter or protein content in aqueous humour. Phentolamine significantly reduced protein leakage into the anterior chamber of the experimental eye. It also significantly inhibited the increase in IOP and protein leakage in the contralateral eye. The present findings demonstrate that a hypertensive inflammatory phase is present in the acute experimental uveitis. The mechanisms of the reaction and the mode of action of phentolamine are discussed.

Decreased ecto-5'-nucleotidase activity in rabbit lymphocytes during experimental lens-induced uveitis

An experimental uveitis was produced by immunizing albino and pigmented rabbits with heterologous (rat) lens protein six times at two-week intervals. After sensitization the anterior lens capsules were disrupted in an operation. After operation the rabbits were examined repeatedly with a slit-lamp. On the seventh day after operation the animals were sacrificed and both eyes were enucleated. The inflammatory reaction in the uveal tract was verified histopathologically. Thymus and spleen lymphocytes were purified using BSA-gradients. Ecto-5'-nucleotidase (AMP-ase) activity on the intact lymphocytes was measured biochemically and B-cells were counted using the fluorescent anti-IgG technique. Purified spleen and thymus lymphocytes were also analyzed using transmission electron microscopy. The AMP-ase activity of purified spleen lymphocytes was significantly decreased in albino rabbits suffering from experimental lens-induced uveitis when compared to that observed in control animals. The AMP-ase activity was also decreased in pigmented rabbits suffering from a very mild uveitis. Moreover, a decreased AMP-ase activity was observed in albino rabbits which were only immunized but not operated on and did not show any signs of uveitis. Differences in neither the B-cell proportions nor the ultrastructure of the purified lymphocytes could be observed in any of these experimental groups. It is proposed that the biochemical change in spleen lymphocytes observed in the present work is a reflection of the general immunological state which in certain conditions may lead to uveitis.

Ecto 5'-nucleotidase activity in lymphocytes in cases of uveitis

This study attempts to demonstrate cellular reactivity in cases of uveitis. Lymphocyte AMPase activity was measured in 59 patients with uveitis of different types, all in the active stage. The patients were divided into 3 groups: 1) anterior uveitis with known disease, 2) anterior uveitis with unknown aetiology, and 3) posterior uveitis. The AMPase activity in peripheral lymphocytes from uveitis patients with known disease (group 1) was significantly decreased in comparison to lymphocytes from controls. Patients having endogenous uveitis (unknown aetiology, group 2) showed heterogeneity concerning their enzyme activity, and no significant changes were demonstrated. A subpopulation of patients with very low AMPase activity in the active stage of their disease could be defined. Patients with posterior uveitis showed no change in their lymphocyte AMPase activity. B-cells were also counted in cell suspension to verify that there was no selective change in the B-cells. Cell suspensions from patients with low and normal AMPase activities were studied by the electron microscope and found to have similar proportions of different types of mononuclear cells. Enzyme deficiencies in lymphocytes were associated with immunological disorders and would reflect dysfunction of lymphocytes. The heterogenous results from patients with endogenous uveitis were interpreted as showing cellular reactivity to ocular damage caused by a variety of mechanisms.

Immune response evoked by antigen injection in the rabbit vitreous combined with immunopotentiation

Intravitreal injection of rabbits with antigen evokes a cell-mediated and a humoral immune response as detected by lymphocyte stimulation, skin testing, and hemagglutination tests. The results of the lymphocyte stimulation test largely correlate with the clinical evaluation of the inflammation process. Rabbits which have been sensitized by Freund's complete adjuvant at the moment of intravitreal antigen injection demonstrate a biphasic cell-mediated immune activity to this antigen. Intradermal or intraocular antigenic challenges of the rabbits 5 weeks following the intravitreal injection evoke responses with the characteristics of an Arthus reaction. At that moment, antigen-sensitized lymphocytes are found in the draining preauricular lymph nodes but not in the contralateral lymph nodes, suggesting separate functioning of these lymph tissues.