الفهرس 
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Abstract
Natural killer (NK) cells are large granular, bone marrow derived lymphocytes that don’t express T or B cell receptors.
NK cells are part of hematopoietic system and are derived from hematopoietic progenitor cells in bone marrow.
NK cells express receptors which when bind to the constant region of Ig, activation signal results in NK cell degranulation and perforin dependent target cell lysis called Antibody Dependent Cell mediated Cytotoxicity.
NK cells have the ability to lyse tumor cells without prior sensitization, they have rapid response to infected or transformed cells either by killing the abnormal cells or by releasing immunomodulatory chemokines and cytokines such as interferon. The chemokine released by NK cells influence the initiation and development of the subsequent adaptive immune response.
NK cell responses result from the integration of signals from both cytokine receptors and NK cell inhibitory and activation receptors.
Natural killer T (NKT) cells are T cells that share properties of both T cells and natural killer (NK) cells.
The development of NKT cells begins during postnatal lymphopoiesis and peaks around 6 weeks of age. NKT cells thought to develop in the thymus and home to secondary lymphoid organs.
The progenitor of NKT cells are bone marrow derived thymocytes that develop in the thymus.
NKT cells exist wherever other T cells are present; in hematopoïetic tissues, Lymph nodes, digestive tract associated lymphoid tissue and in the dermal tissue.
The frequency of NKT cells in the peripheral blood lymphocytes ranges from 0.1 to 0.3% in most healthy subjects.
Upon activation, NKT cells are able to produce large quantities of interferon-gamma and IL-4, as well as multiple other cytokines and chemokines (such as IL-2, Interleukin-13, Interleukin-17, Interleukin-21).
NKT cells might produce anti-inflammatory cytokines, depending on the type of signals they receive.
NK cells play a critical role in human asthmatic response, as they facilitate sensitization in the initial allergic asthmatic response to either self or exogenous glycolipid. When NK cells become activated, they release various types of cytokines which are responsible for AHR.
Blocking of the action of NK cells and their cytokines is the future treatment of bronchial asthma.
There is evidence that the imbalance between the activating and inhibitory receptors of NK cells is associated with development of bronchial carcinoma.
Expansion and activation of NK cells wil be the key factor in treatment of bronchial carcinoma instead of chemotherapy and radiotherapy.