Khalid F. Tabbara

Human conjunctival mast cells: Distribution of MCT and MCTC in vernal conjunctivitis and giant papillary conjunctivitis

The distribution and concentration of human tryptase-positive, chymase-negative mast cells (MCTS) and tryptase-positive, chymase-positive mast cells (MCTCS) were examined in conjunctival biopsy specimens from subjects with active vernal conjunctivitis (VC; n = 7), giant papillary conjunctivitis (GPC; n = 6), and allergic conjunctivitis (AC; n = 5), and from asymptomatic soft-contact lens wearers (SCL; n = 6) and normal control individuals (n = 19). Carnoys fixed tissue sections were stained by a double immunohistochemical method using a biotinylated mouse monoclonal antichymase antibody with immunoperoxidase, followed by an alkaline phosphatase-conjugated mouse monoclonal antitryptase antibody. Epithelial mast cells (MCs) were found in all VC specimens (96% MCTCs) and in three GPC specimens (100% MCTCS) but in none of the other groups. In the substantia propria, MCTCS were the predominant type of MC observed in all specimens, accounting for 95% of the total MCs in the normal control group and 100% of the total MCs in the subjects with GPC, AC, and SCL. No significant differences were found in the total MC concentration of the substantia propria among the normal control subjects (11,054 +/- 6327 MCs per cubic millimeter), subjects in the SCL group (13,168 +/- 4685 MCs per cubic millimeter), subjects with GPC (17,313 +/- 8500 MCs per cubic millimeter), and subjects with AC (15,380 +/- 5660 MCs per cubic millimeter). In subjects with VC, the percentage of MCTs (18% +/- 13%) and the total MC concentration (24,689 +/- 18,978 MCs per cubic millimeter) in the substantia propria were significantly increased as compared to the normal control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of Ocular Toxoplasmosis with Clindamycin and Sulfadiazine

Seventeen patients with active toxoplasmic retinochoroiditis were treated for four weeks, seven with clindamycin alone and ten with a combination of clindamycin and sulfadiazine. The follow-up period ranged from six months to four years. Results of the Sabin-Feldman dye test were positive in all patients. Five of the seven patients treated with clindamycin alone showed improvement two weeks after treatment was begun, while eight of the ten patients treated with combined clindamycin and sulfadiazine showed both subjective and objective improvement within ten days and signs of healing within three weeks. Since clindamycin and sulfadiazine operate on unrelated metabolic pathways of Toxoplasma, they may act synergistically. A regimen consisting of this combination may be appropriate for the treatment of ocular toxoplasmosis.

Chlorambucil in Behçet's Disease: A Reappraisal

Ten patients with Behçets disease were treated with chlorambucil alone. At the therapeutic drug level of 0.2 mg/kg, seven patients developed oligospermia and three patients developed azoospermia. A 30-year-old patient underwent a testicular biopsy two years after the cessation of therapy. Histopathology revealed evidence of testicular atrophy. Fifteen (75%) out of 20 eyes had a visual acuity of 20/200 or less following therapy. It is concluded that chlorambucil should not be used as the first line of therapy in Behçets disease and that its long term benefits in patients with Behçets disease should be reevaluated.

Ocular Ferning Test: A Qualitative Test for Mucus Deficiency

A new qualitative test for the study of conjunctival mucus has been developed. Conjunctival scrapings were obtained from 196 patients. Microscopic mucus ferning (arborization) was observed in 148 (91%) patients with various forms of acute conjunctivitis. Six patients (18%) with cicatrizing conjunctivitis (diffuse conjunctival cicatrization, ocular pemphigoid, Stevens-Johnson syndrome) had mucus ferning in their conjunctival scrapings specimens. Mucus ferning was significantly absent (P less than 0.005) in patients with diffuse conjunctival cicatrization when compared to mucus ferning in other forms of conjunctivitis. Ocular mucus ferning test is a simple inexpensive office test for the evaluation of patients with mucus deficiency.

The Role of Hypersensitivity Reactions to Toxoplasma Antigens in Experimental Ocular Toxoplasmosis in Nonhuman Primates

To assess the role of ocular hypersensitivity reactions to Toxoplasma antigens in previously sensitized ocular tissues, we used a nonhuman primate model of ocular toxoplasmosis. Each eye of eight monkeys was inoculated with living Toxoplasma organisms into the inner retinal layers. All eyes developed necrotizing retinochoroiditis. Healing of the lesion occurred with the formation of a retinochoroiditic scar. Four months later, Toxoplasma antigens were injected through the right internal carotid artery. Four weeks after this, Toxoplasma antigens were inoculated into the left retina. Iritis, vitritis, and retinal edema occurred in response to the administration of the antigens, but no recurrent necrotizing retinochoroiditis was produced in this model. These findings suggested that hypersensitivity to Toxoplasma antigens does not play a major role in triggering recurrences of toxoplasmic retinochoroiditis in nonhuman primates.

Thygeson's Superficial Punctate Keratitis

Thygesons superficial keratitis is a chronic disease of the cornea characterized by focal epithelial lesions. We studied 45 cases of Thygesons superficial punctate keratitis. Twenty-eight were male and 17 were female patients. The disease had been active in our patients from one month to 24 years. The clinical findings, course, outcome, and response to therapy were studied. Viral cultures and microscopic studies were performed on the corneal epithelial scrapings from ten cases. The average course of the disease was prolonged in patients who received topical steroid therapy. Subepithelial opacities were seen more frequently in patients who had received treatment with idoxuridine (IDU).

Vernal Keratoconjunctivitis and Keratoconus

The association of keratoconus with atopic disorders has been described in several uncontrolled clinical studies. 1-3 Although keratoconus is known to occur in patients with atopic dermatitis, to the best of our knowledge, the association of keratoconus with vernal keratoconjunctivitis has not been previously reported. We treated two patients with severe unilateral vernal keratoconjunctivitis and unilateral keratoconus.

Retinal vasculitis in ocular toxoplasmosis in nonhuman primates.

Six monkeys had prior systemic immunization followed by intraretinal challenge to each eye with Toxoplasma antigens. All eyes developed iridocyclitis, vitritis, and retinal edema, but no necrotizing retinochoroiditis. One-half of the eyes were then challenged with living organisms and the other one-half with Toxoplasma antigens. All eyes developed iridocyclitis, vitritis, and retinal edema, but no necrotizing retinochoroiditis. Four months later, the right eye of each monkey was challenged with living Toxoplasma organisms injected intraretinally. Each injected eye developed iridocyclitis, vitritis, and retinal edema 24 hours after injection, and all developed a retinal vasculitis 6 days after injection. One injected eye developed a papillitis. A subcutaneous booster of living Toxoplasma organisms in four of the monkeys failed to produce a reactivation of the iridocyclitis, vitritis, and vasculitis. These findings suggest that hyperimmunization provides protection against the development of a necrotizing toxoplasmic retinochoroiditis in nonhuman primates and that it may lead to retinal vasculitis and iridocyclitis. This study also serves as an animal model of retinal vasculitis in ocular toxoplasmosis.Six monkeys had prior systemic immunization followed by intraretinal challenge to each eye with Toxoplasma antigens. All eyes developed iridocyclitis, vitritis, and retinal edema, but no necrotizing retinochoroiditis. One-half of the eyes were then challenged with living organisms and the other one-half with Toxoplasma antigens. All eyes developed iridocyclitis, vitritis, and retinal edema, but no necrotizing retinochoroiditis. Four months later, the right eye of each monkey was challenged with living Toxoplasma organisms injected intraretinally. Each injected eye developed iridocyclitis, vitritis, and retinal edema 24 hours after injection, and all developed a retinal vasculitis 6 days after injection. One injected eye developed a papillitis. A subcutaneous booster of living Toxoplasma organisms in four of the monkeys failed to produce a reactivation of the iridocyclitis, vitritis, and vasculitis. These findings suggest that hyperimmunization provides protection against the development of a necrotizing toxoplasmic retinochoroiditis in nonhuman primates and that it may lead to retinal vasculitis and iridocyclitis. This study also serves as an animal model of retinal vasculitis in ocular toxoplasmosis. RETINA 4:182-188, 1984

Effect of immunization with attenuated Mycobacterium bovis on experimental toxoplasmic retinochoroiditis.

Administration of attenuated Mycobacterium bovis (Bacillus Calmette-Guérin or BCG) provides nonspecific resistance to a variety of microbial infections and tumors. This is associated with a state of augmented immunologic responsiveness. Mustering defenses against intracellular parasites, such as Toxoplasma gondii, presents a special problem that can be met only by measures that alter the intracellular environment. Our study was designed to evaluate the effect of prior immunization of rabbits with BCG on experimental toxoplasmic retinochoroiditis. One group of rabbits was immunized by the intravenous administration of BCG, another group by the retrobulbar injection of BCG, and a third group, unvaccinated, served as a control. Intravenous immunization provided significant protection against Toxoplasma organisms injected into the suprachoroidal space. In the immunized rabbits, the onset of Toxoplasma retinochoroiditis was delayed and the severity of the disease reduced. Although Toxoplasma was isolated from the chorioretinal tissues of both BCG-immunized and control rabbits, Toxoplasma antibody was not (with one exception) detected in the sera of BCG-immunized rabbits. While vaccination by the retrobulbar route produced little or no effect, intravenous administration of BCG provided nonspecific resistance to Toxoplasma retinochoroiditis in rabbits.

Minocycline in the chemotherapy of murine toxoplasmosis

The effects of minocycline alone or in combination with sulphadiazine were evaluated against acute murine toxoplasmosis and compared with the efficacy of pyrimethamine and sulphadiazine. The date presented show that mice could be protected from acute toxoplasmosis by minocycline, in spite of using a virulent strain of Toxoplasma gondii, a large inoculum, and a delay in the administration of the drug. Acute toxoplasmic infection in mice could be eradicated by aminocycline--sulphadiazine combination, which was found to be as effective as pyrimethamine--sulphadiazine combination therapy.