X Her brotherâs illness forced her to explore feelings that had lied dormant for some time. â â¦. that had lain dormantâ¦ [past perfect of lie (1)]. X I laid down on my bed and went to sleep. â I lay down on my bedâ¦ [simple past of lie (1)]. X Sheâs laying flat on her back, out for the count. â Sheâs lying flat on her backâ¦ [present continuous of lie (1)]. X When she died, she was lain in an ornate wooden coffin. â â¦she was laid in an ornate wooden coffin.
The receptors match only one specific antigen. White blood cells called lymphocytes originate in the bone marrow but migrate to parts of the lymphatic system such as the lymph nodes, spleen, and thymus. There are two main types of lymphatic cells, T cells and B cells.he receptors match only one specific antigen. White blood cells called lymphocytes originate in the bone marrow but migrate to parts of the lymphatic system such as the lymph nodes, spleen, and thymus. There are two main types of lymphatic cells, T cells and B cells.
The specialized cells of the immune system, called lymphocytes, are initially produced in the bone marrow. Lymphocytes mature either in the bone marrow to become B cells or in the thymus to become T cells. B cells produce antibodies that circulate in the blood or the lymphatic system. Antibodies attach to foreign antigens and mark these invaders for destruction by other cells in the immune system. T cells have two major roles. They can become cytotoxic T cells capable of destroying cells marked as foreign.