Ipsilateral submandibular lymphadenectomy does not prolong orthotopic corneal graft survival in mice

To explore the impact of selective lymphadenectomy on the outflow from the outer eye and corneal graft survival in mice.

BALB/c mice underwent submandibular lymphadenectomy either on the left side 7 or 21 days before the experiments or bilaterally 7days in advance. First, ^99mTc colloidal albumin (Nanocoll) was given as a subcutaneous lower-lid, upper-lid or subconjunctival injection, and count rates were determined 24 h later in the eyes, submandibular lymph nodes, spleen, liver and blood. Second, corneal graft survival was assessed in lymphadenectomised and control mice, and IFN-γ secretion was determined in draining lymph nodes at the time of transplant rejection.

Following subconjunctival Nanocoll injection, count rates/min/mg tissue were significantly higher in the ipsilateral submandibular lymph node than in the other tissues or blood (<0.01). Ipsilateral lymphadenectomy prior to injection resulted in considerably increased count rates in contralateral nodes (P<0.01), which were higher after injections into upper than into lower lids (P=0.004). Bilateral submandibular lymphadenectomy led to enhanced count rates in the eyes, blood, spleen and liver (all P<0.01). Removal of the ipsilateral lymph node prior to corneal transplantation did not prolong allograft survival (P>0.05) and considerably increased IFN-γ secretion in contralateral nodes after prior removal of the ipsilateral ones paralleled transplant rejection.

In mice, removed submandibular lymph nodes are functionally completely replaced by the contralateral nodes. These studies demonstrate for the first time lymphatic drainage crossing the midline of the body. Consequently, unilateral lymphadenectomy does not improve corneal graft survival.