A 32-year-old woman presents with a 3-month history of progressive weight loss, heat intolerance, palpitations, and insomnia. She also describes gritty sensation and redness in her eyes. Physical examination reveals a diffusely enlarged, smooth, non-tender thyroid gland, a resting heart rate of 110 bpm, and bilateral exophthalmos. Laboratory studies show suppressed TSH and elevated free T4. A radioactive iodine uptake scan demonstrates diffusely increased uptake throughout the gland. Which of the following immunologic mechanisms best explains her clinical presentation?