MACROPHAGE INFILTRATION AT THE NEUROMUSCULAR-JUNCTION DOES NOT CONTRIBUTE TO ACHR LOSS AND AGE-RELATED RESISTANCE TO EAMG

Aged rats resistant to acetylcholine receptor loss in passive transfer experimental autoimmune myasthenia gravis (EAMG) do not reveal infilt rating macrophages at the neuromuscular junction (NMJ) as observed in susceptible rats. It was investigated whether this age-related resista nce is due to impaired macrophage function in these aged rats. Reconst itution of aged rats with bone marrow from young donors did not lead t o macrophage infiltration, nor did it abolish resistance to EAMG. Subs equently, it was investigated whether macrophages are a primary cause of acetylcholine receptor (AChR) loss in EAMG or are attracted to the NMJ secondary to tissue damage. In lethally irradiated young susceptib le rats infiltrating macrophages were absent from the NMJ. However, si milar AChR losses were observed in irradiated and non-irradiated rats. These results suggest that macrophages do not contribute to acetylcho line receptor loss in the effector phase of passive transfer EAMG and that age related resistance to passive transfer EAMG is not primarily determined by the absence of infiltrating macrophages.