Questions of presentation

Article Abstract:

A recent meeting in New York City highlighted the tremendous complexity that underlies an immune response to a foreign antigen. A great deal has been learned in recent years, but key questions remain unanswered. To a first approximation, the net result of the immune response may be thought of as cellular or humoral. A cellular response might involve T cells attacking a virus-infected cell within the tissues; an example of a humoral response might be antibodies covering the body of an invading bacteria and rendering it susceptible to puncture by the complement chain. In either case, the response must be learned, and this learning involves the appropriate presentation of antigen to immune cells, a procedure accomplished by products of the genes of the major histocompatibility complex (MHC). The products, called human leukocyte antigens (HLA), exist in two main classes. Class I molecules are found on the surface of most cells. If the cell should be infected by a virus, peptide fragments of the viral proteins will be bound by the class I molecules, which will then hold them out for recognition by a subset of T cells, the CD8-positive T cells. Although it is believed the class I molecule binds peptides which have been synthesized within the cell itself, it is not entirely clear how the peptide gets to the surface. Are the peptide fragments generated within the cytoplasm, or are intact molecules transported through the secretory pathway and processed there? Once the peptides are formed, however, they seem to bind rapidly to the class I molecule, an event which probably occurs before the molecule has left the Golgi apparatus. Class II molecules present antigens which are made externally to the cell. External proteins must, then, in some way be internalized before they are processed and presented. Cells with class II molecules internalize foreign antigens, probably in endosomes where they are proteolyzed. The peptides then bind class II molecules which present to another type of T cell, the CD-4 helper T cell. This cell responds by replicating and secreting hormones to stimulate other immune cells. An argument exists as to the origin of antigen-binding class II molecules; some investigators believe that they are newly synthesized molecules, others believe that in order to bind antigen, the class II molecules must first have been on the cell surface, and then recycled. (Consumer Summary produced by Reliance Medical Information, Inc.)

HLA histocompatibility antigens, HLA antigens, editorial, Histocompatibility antigens

---

HLA-DR molecules from an antigen-processing mutant cell line are associated with invariant chain peptides

Article Abstract:

Human T2 cell lines containing mutations of the major histocompatibility complex (MHC) class II molecules cause a nested set of peptides from the invariant chain to be linked to the class II molecules. The invariant chain acts with MHC molecules in the endoplasmic reticulum and affects antigen processing. Class II-associated invariant chain peptides (CLIP) and HLA-DR3 take part in the interaction between MHC mutants and the invariant chain. CLIP probably determines what parts of the invariant chain prevent class II molecules from acting as binding sites.

Peptides, Antigens

---

Proteasome subunits encoded in the MHC are not generally required for the processing of peptides bound by MHC class I molecules

Article Abstract:

The proteins LMP2 and LMP7 are not required for normal peptide processing and expression of stably processed major histocompatibility (HMC) class I molecules. Proteasomes are therefore not involved in antigen processing, as has been suggested. LMP2 and LMP7 may play some other, more subtle role, however.

Genetic aspects, Antigen presenting cells

Similar abstracts:

• Abstracts: Mutations in Cu/Zn superoxide dismutase gene are associated with familial amyotrophic lateral sclerosis. MOD-1 is a serotonin-gated chloride channel that modulates locomotory behaviour in C. elegans
• Abstracts: Comparison of two types of metapopulation models in real and artificial landscapes. Consensus versus conservation in the upper Colorado River Basin Recovery Implementation Program
• Abstracts: Comparison of two types of metapopulation models in real and artificial landscapes. part 2 Effects of Coastal Lighting on Foraging Behavior of Beach Mice
• Abstracts: Stimulation of protein tyrosine phosphorylation by the B-lymphocyte antigen receptor. Tolerance: a second mechanism
• Abstracts: Circulating CD8+ cytotoxic T lymphocytes specific for HTLV-I pX in patients with HTLV-I associated neurological disease

This website is not affiliated with document authors or copyright owners. This page is provided for informational purposes only. Unintentional errors are possible.