T cells Flashcards
Antigen presenting cells (APC)
Dendritic cells
B cells (antibody and APC)
Selected Macrophages
Monocytes
Keratinocytes
How are MHC (major histocompatibility complex) proteins (antigens) coded
by a number of genes located as a cluster on a part of a chromosome
3 types of MHC proteins or antigens
Class I-all nucleated cells (avian RBC)
Class II-present on selected cells
Call III-complement components and sex limited proteins
Class I antigens
Cytotoxic T cells recognize abnormal targert calls via class I antigens which becomes associated with foreign antigens
If MHC antigen is increased/decreased
Immune response with increase/decrease respectively
MHC
complex is inherited as a block
Proteins have a highest rate of mutation
proteins bind to processed antigenic peptides
How are antigens presented to T cells
Antigens taken in by antigen presenting cells(APC) are chopped into small pieces and presented on their surface by MHC proteins to T cells
Types of Antigens
EXogenous (coming into the body EXternally)
ENdogenous (IN the body)
Processing and presentation of Exogenous Antigens
Antigen appears
Antigen chopped to peptide level
Peptide binds to MHC class II
Back to cell membrane to be displaced
Exogenous antigens associate with MHC class II
Processing and presentation of Endogenous antigens
processed endogenous antigens associate with MHC class I
Lymphocyte structure
Located in the blood, lymph and lymphoid tissue
5-15 micrometers in diameter
most of the cell contains nucleus (thin rim of cytoplasm containing free ribosomes, mitochondria)
Specific Immunity involves
T and B lymphocytes
T lymphocytes
CD4 and CD8
T cell surface markers
T cell receptor (antigen recognition, alphabeta and gammabeta)
CD3 (Signal transduction)
CD4 (Helper) or CD8 (cytotoxic)
CD28 (co-stimulatory molecule)
CD40L (co-stimulatory molecule)
Cytokine receptor (IL-2, INF gamma)
T cell selection
majority of developing T cells die within the thymus. Only those cells that are competent leave the thymus. Cells that die include defective cells, cell that react with self-antigens(negative selection). Most emigrated T cells (positive selection)
Cortex
most immature immigrants from bone marrow-95% die
Medulla
Mature thymocytes ready to exit thymus or T cell
Immature cells
lack CD4 or CD8
double positive
CD4+CD8+
Mature cells
CD4+CD8- (helper)
CD4-CD8+ (cytotoxic)
Types of CD4+ (T helper)(Th)
Th-1
Th-2
Th-17
Treg
Th-1
Participates in delayed types hypersensitivity (DTH)
TH-1 cells primarily secrete IFN-gamma and IL-2
immunity against INTRAcellular pathogen
(antibody can not penetrate a cell)
Th-2
Help other cells (B or T cells) by secreting interleukin
Th-2 cells primarily secrete IL-4, IL-6, and IL-10
IL-4 attract B cells and make alot of antibodies outside the cell
Th-17
regulation of inflammatory response
Th-17 cells primarily secrete IL-17, IL-22 and TNF-alpha
pro inflammatory cytokine
Treg
Regulation of immune response by suppressing it
Primarily secrete TGFbeta
ability to interact with all cells
bring back to homeostasis
