It is referred to as "non-specific" because it generally attempts to stop the spread of all types of invaders. (Kuby, 1996)
The latter type consists of two categories: cell-mediated immunity and antibody-mediated (humoral) immunity. It is the stronger one of the two types but takes several hours or even days to become fully activated. It is referred to as "specific" because it responds differently to every other foreign pathogen. (Hariharan, 2006)
Lymphocytes, a class of White Blood Cells, are a vital part of the acquired immune system, being responsible for the whole reaction. They are produced in the primary lymphoid organs and then migrate to the secondary lymphoid organs where they recognize antigens of foreign bodies by the help of membrane receptors specific to the antigens. Two major classes of lymphocytes take part in the acquired immunity: B-Cells (B lymphocytes) and T-Cells (T lymphocytes). (Alberts, Bray, Lewis, Raff, Roberts, Watson, 1994), (Linnemeyer, 1993)
Precursors of T-cells originate in the foetal liver and yolk sac during the embryonic life, and migrate to the bone marrow after birth. ...