Figure 2. Ultrastructural findings in control lymphoblastoid cells (LC) (A, B) and LC derived from MSS patients (C-V).

(A, B) Regular organelle structures in LC derived from healthy probands. Scale bars in A = 5 μm; in B = 2 μm. (C) Hyperchromasia of the nucleus and cytoplasmic accumulation of electron-dense material (white arrow) in a LC derived from a MSS patient. Scale bar = 7.5 μm. (D) Higher magnification of (C) emphasizing widened rough ER (black arrow) and outfoldings of the lifted-off nuclear envelope (asterisk) as well as accumulation of vesicular structures partially filled with electron-dense material. Scale bar = 1 μm. (E) Another representative MSS patient- derived LC presenting with hyperchromasia of the nucleus, increased outfoldings of the lifted-off nuclear envelope, irregular accumulation of electron-dense material within the nucleoplasm and large cytosolic vacuoles. Scale bar = 7.5 μm. (F-I) proliferation of disorganized mitochondria. Cell depicted in the inset G in addtion to disorganized mitochondria also shows (electron-lucent) vacuole. Scale bars in F = 5 μm; in H = 4 μm; in G, I = 10 μm. Occasionally accumulation of myelin-like autophagic material (white arrows in H, J-M). Scale bars in H, J = 4 μm; in K, L = 7 μm; in M = 2 μm. (M, N) show nuclei with “cytoplasmic halos” partially filled with abnormal mitochondria (M). Scale bar in N = 6 μm. (O, P) Nuclear envelope protrusions (asterisks) and considerable vesicular proliferations. Scale bars in O = 3 μm; in K = 7 μm. (Q, R) Irregularly shaped/lobulated and (S, T) splitted/fragmented nuclei. Scale bars in Q = 7 μm; in S, T = 5 μm.