cell mediated innate immunity

Innate lymphoid cells

ILC have lymphoid characteristics (like B & T) but lack antigen specificity

develop in bone marrow from the same common lymphocyte progenitor, then migrate to lymphrid tissue and peripheral organs

3 subgroups of ILCs

1. Group 1: Include ILC 1 and natural killer cells. Uk cells are present in circulation and in tissues. ILCs are largely tissue resident cells

2. Group 2: Participate in mucosal immunity and produce IL- 4, IL-5, IL-13

3. Group 3: Produce several cytokines that induce production of chemokines and antimicrobial peptides against extracellular bacteria and fungi.

Nk cells

kill certain tumor and virus infected cells without specific immunizations. They get activated pretty early in an infection

activated by cytokines 

Three modes of killing target cells by activated NK cells

1. Cytotoxic granules → grannymes and pore-forming protein perforin are released onto the target cells to penetrate the cell to induce programmed cell death → caspase path way

2. TN F-related apoptosis inducing ligand (TRAIL) → NK cells express TRAIL, Which interact with death receptors on target cells to activate caspase 8 and induce apoptosis

3. Antibody dependent cellular toxicity → NK cells express Fc receptors, which bind to antibody coated target cells and induce release of cytotoxic granules by Nk cells

NK cell receptor families

• killer cell immuneglobalin -like receptors

• killer cell lectin like receptors

• Natural cytotoxicity receptors