Abstract
Purpose:
To functionally test if immune processes are both initiated and capable of causing damage in glaucoma we carried out adoptive transfers between mouse models of glaucoma and normal recipient mice.
Methods:
B6.Sh3pxd2bnee (nee), immune-deficient B6.129S7-Rag1tm1Mom/J/nee (nee/Rag1), myocilin transgenic B6.Tg-MYOCY437H (MYOC), or C57BL/6J wild-type (B6) mice served as donors. Splenocytes (5x106) or FACS sorted CD19 (1.5x106) and CD3 (1x106) lymphocyte fractions were transferred to 2-month-old B6 recipients (rec, n>5 animals/group). Intraocular pressure (IOP) was monitored by tonometry and RGC density (RGC/mm2) was evaluated in retinal wholemounts via gamma-synuclein immunostaining. Naïve B6 mice served as a control (ctrl). In additional experiments, OCT imaging was conducted, and transferred immune cells expressing DsRed were spatiotemporally tracked in recipients. Differences were evaluated using Tukey’s post-hoc test.
Results:
Transferred splenocytes from both nee or MYOC mice elicit significant loss of RGC in recipient mice after 4 months when compared to ctrl or B6 recipients (RGC/mm2 in ctrl: 2290±254, B6 rec: 2284±299, nee rec: 1886±267, p<0.03; MYOC rec: 1798±152, p<0.02). Transfer of nee/Rag1 splenocytes did not induce loss of RGC (nee/Rag1 rec: 2423±383 RGC/mm2) Animals having received nee T-cells also display significantly reduced RGC density when compared to B6 T-cell recipients (RGC/mm2 in B6 T-cell rec: 2251±221 vs. 1831±245 in nee T-cell rec, p=0.004). Transfer of nee B-cells leads to a modest reduction of RGC (RGC/mm2 in B6 B-cell rec: 2259±266 vs. 1968±317 in nee B-cell rec, p=0.07). Transferred cells were frequently found integrated into the recipients’ spleens. DsRed+ nee lymphocytes were occasionally observed in the retina of recipient mice and appeared to be engaged in cell-cell interaction with microglia. Elevated IOP, disruption of retinal integrity, or significant leukocyte infiltration was not observed in any recipient animals.
Conclusions:
These data demonstrate that glaucomatous RCG loss elicits an adaptive immune response that is capable of promoting IOP-independent RGC loss following adoptive transfer. The immunopathology in recipients seems to be primarily T-cell dependent. It is conceivable that once established such an autoimmune response could lead to continued RGC loss in glaucoma patients despite significant reduction in IOP.