Cholinesterase activity in some human lymphatic organs.

(1) Cholinesterase activity was investigated in some human lymphatic organs (palatine tonsil, 'normal' spleen, 'bilharzial' spleen, thymus, lymph node and appendix) using GOMORI'S modification of KOELLE and FRIEDENWALD'S thiocholine iodide method, hydrolyzing acetylthiocholine iodide and butyrylthiocholine iodide. (a) Acetyl- and butyrylcholinesterases seemed to be different enzymes; but when they have the same pattern of activity, the latter generally offers a weaker reaction. (b) All the lymphatic follicles of the tonsil, those found in the cortex of the cervical lymph nodes as well as those present in the appendix, were stainable with both acetyl- and butyrylcholinesterase. (c) Acetylcholinesterase activity was not demonstrated in the Malpighian bodies of the 'normal' spleen, but the reaction was strongly present in the blood vessels (including the central arterioles) as well as in the capsule and the different components of the trabecular system. (d) In 'bilharzial' splenomegaly a relatively strong activity started to appear in the Malpighian corpuscles, manifested as a brownish precipitate in their centres. Also some patchy positive areas began to make their appearance in the tissue of the red pulp and had a particular arrangement around the Malpighian corpuscules, in such a way as to 'wall them off' from the tissue of the red pulp. (e) In the thymus no acetylcholinesterase activity was encountered, except in Hassal's corpuscles and in the trabeculae between the thymic lobules. (2) The data obtained in this work were discussed in relation to previous works in other laboratories and it seems that a species difference exists. (3) Cholinesterases may be present in the lymphatic tissue in order to get rid of some potentially toxic esters resulting from the necrobiotic phenomena accompanying the high mitotic activity found especially in the germinal centres of the lymphoid follicles. (4) There are many unanswered questions about the coexistence of the phosphatases and cholinesterases in the same places; their concomitant association in the lymphatic tissue may represent a special case within the framework of a more general mechanism.