Introduction Course to Porcine Immunology

THE OTHER LYMPHOCYTES


There are other lymphocytes of great importance in the natural or innate immune responses in the pig in addition to  T g-d lymphocytes, (formerly known as null cells) and which in fact are a type of T lymphocytes. These are the NK cells.

NK cell.

 NK cells present a cytotoxic activity against cells infected by viruses and tumor cells, even though they do not recognize them by a specific antigenic stimulus (NK cells do not express TcR). This cytotoxic activity is not limited by SLA, as T lymphocytes (CD 8) Their activation mechanisms begin when they recognize, in a natural way, cells that do not express SLA in a correct way, as happens with most virus infected cells. Apart from this, they secrete soluble mediators (cytokines) such as Tumor Necrosis Factor (TNF), interferon g. This allows the stimulation of various lymphoid mechanisms. (Chapter 6).

NK cell expressing the receptor for the Fc fraction of immunoglobulins.


In the porcine species, NK cells are small or medium sized lymphocytes, without granules, in contrast with murine and human species, where NK cells are large, granulated lymphocytes. Porcine NK cells react with monoclonal Antibodies against porcine T lymphocytes belonging to groups CD 2 and CD 8, but not against those of groups CD 3, CD 5 and CD 6. In addition to this, the reaction with CD 8 is lower that of T cytotoxic lymphocytes CD 8+. The best monoclonal antibody for the study of porcine NK cells belongs to the CD 16 group. 

NK cells have a role in the natural or innate immune response. These cells appear in a larger proportion in young animals, and they diminish as the animal grows. This means that the role of NK cells is related to natural or innate immune response mechanisms, and not to those mediated by a specific antigenic stimulation (acquired immunity).

CHARACTERISTICS OF NK CELLS
  • Receptor for Fc fraction of Immunoglobulins
  • Cytokines secretion: TNF and If g
  • Do not express TcR
  • CD for NK: CD 16

 

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