We were interested to read the article by
Ongkosuwito et al.,
1 whose work expands the knowledge on
cytokine expression in intraocular fluids. They used enzyme linked
immunosorbent assay to examine the cytokine profile in the vitreous or
aqueous humor of 44 eyes with infectious uveitis. The results were
compared to 51 control samples. Increased interleukin (IL)-6 levels
were found in 44 control eyes and 43 eyes with infectious uveitis.
IL-10 was detected in 10 eyes with acute retinal necrosis
(ARN) and 13 eyes with toxoplasmosis, but in only 3 control
samples. Interferon (IFN)-γ was detected in 20 eyes with infectious
uveitis and one control eye. IL-2 was found in 3 noninfectious uveitis
control samples but in only one infectious uveitis case. IL-4 was
undetectable in all eyes. On the basis of their results, they were
unable to demonstrate a salient role for either a T-helper type 1 or a
T-helper type 2 response in the pathogenesis of nonexperimental
uveitis.
In their discussion the authors reference one of our early
publications
2 in which we suggested that the finding of
IL-10 in the vitreous can aid in the diagnosis of primary intraocular
lymphoma (PIOL) because it is absent in eyes with uveitis. They also
mentioned that we reported 1 patient with ARN in whom IL-6 but not
IL-10 was detected. They speculated that the absence of IL-10 in our
ARN case was due to obtaining the vitreous sample late in the disease
course.
In a subsequent article
3 we reported that PIOL is
strongly associated with an increased IL-10 to IL-6 ratio (greater than
1.0). Four of 13 uveitis patients had both elevated vitreal IL-6 levels
and increased IL-10. In these four patients the IL-10:IL-6 ratio was
less than 1.0 (0.13, 0.26, 0.67, 0.90), whereas, the vitreal IL-10:IL-6
ratio in all patients with PIOL was greater than 1.0.
To date we have performed cytokine analysis with ELISA on 52
vitrectomy specimens from 50 patients with infectious and noninfectious
uveitis. We have found elevated IL-6 levels in 31 samples (59%) but
elevated IL-10 in only 6 (12%). In those 6 with increased IL-10
levels, the IL-6 was higher, with a calculated IL-10:IL-6 ratio less
than 1.0 in all. Of 5 patients with ARN, only 2 had elevated IL-10
levels, whereas 4 had increased IL-6. Although IL-6 levels were
increased in both toxoplasmosis cases, only one had detectable IL-10.
We are unable to establish a correlation between the duration of
disease at time of the vitrectomy and the IL-10 level in the patients
with ARN. We calculated the vitreal IL-10:IL-6 ratio of the patients
with infectious uveitis reported in Ongkosuwito’s study. All, except 2
(1.04, ARN; 1.91, inactive toxoplasmosis), had a ratio less than 1.0.
Recently, we had a case of PIOL in which the vitreal IL-10:IL-6 ratio
was less than 1.0.
4 We speculated that this represented an
early stage in the tumor course. The presence of IL-10 in the eyes of
uveitis patients is not diagnostic of malignancy; however, in those
cases in which the vitreal IL-10 level is higher than the IL-6 the
diagnosis of a PIOL should be strongly considered.