Entry No:Each entry of database has been given a unique 5-digit decimal identity number

MHC allele:It contains the MHC type or specific MHC alleles. The MHC molecules are coded by the clusters of the genes. They are primarily responsible for graft rejection. In case of humans, the MHC molecules are known as histocompatibility leukocyte antigens (HLA).

MHC Allele Sequence:The database contains the amino acid sequence of most of MHC molecules in FASTA format, with link to IMG/HLA-DB and ENTREZ database (4). This field has facility of searching for the exact or approximate search of MHC allele sequence. Thus user can access the complete information on Human MHC alleles including nucleotide sequence and alignment available at IMGT/HLA-DB.

Experimental Method: This includes the experimental methods used for exploring peptide MHC binding and T cell activity properties. The binding of peptides to MHC are mainly studied by competitive binding assay , Peptide elution , MHC reconstitution assay , stabilisation assay , mass spectroscopy etc. The T cell activity of peptides can be determined by assays like Cytotoxicity assay, Proliferation assay, cytokine release assay, ELISPOT assay, etc. The MHC binding properties can be indirectly determined by measuring T cell activity because all the T cell epitopes are MHC binders.

Peptide Sequence:Each entry has single amino acid peptide sequence as reported in the literature. The peptide sequence is internally linked so that all the entries of database having matching sequence can be extracted. The database has the repetition of peptide sequences as a single sequence can bind with many MHC alleles.

Binding affinity: The binding affinity of peptides to MHC is divided into four groups by using the parameter similar to MHCPEP database(Brusic et al 1998). The peptides having IC50nm more than 50,000 considered as non-binders. In some entries peptides are divided in high, moderate, low and non-binders according to the parameters mentioned by authors in papers. This field may have peptides where T cell activity is known but binding affinity is undetermined These peptides are considered MHC binders as MHC binding is prerequisite for a T cell epitope.

T cell Activity:is a measure of immunogenic potency of a peptide. This is determined in whole database by using the same parameters as used in MHCPEP database (Brusic et al .,1998). The parameter used by the authors of the papers for determining immunogenic potential of a peptide also taken in consideration. T cell activity is "YES,?" where the peptide is immunogenic but its PD50 is unknown.

MHC Class: The hundreds of genes encoding MHC are divided into 3 groups, gene involved in class I, class II and class III.. This field denotes the group of genes encoding MHC molecules. The host organism field specify the organism in which specific MHC allele occurs.

MHC Structure: contains information about the tertiary structure of MHC alleles. This field contains the name of PDB file corresponding to MHC allele or MHC allele and peptide complex. The database has summary of PDB files, which are externally hyperlinked to PDB database.

Source protein: This field specifies the antigenic protein from which particular peptide is obtained. The most of the entries contains the exact numerical position of the immunogenic peptide in antigenic proteins.

Reference Database: This field has the codes of the parent proteins having sequence that matches with the immunogenic or MHC binding peptide sequence. The codes of the proteins are obtained by searching latest version of Swissprot ( ) database. The codes of the proteins are internally linked to FASTA format of antigenic sequence which is further hyper linked to SWISSPROT and ENTREZ database.

Antigenic structure: contains the PDB codes of the proteins having primary sequences that match the MHC binding peptide sequences. The database contains the summary of PDB files, which is fully hyperlinked to OCA database.

Anchor position: means the position of the anchor amino acids relative to N-terminal. This is mostly determined by the substitution analysis of the antigenic peptide. The value of field is "Not Determined" where anchor positions in peptide sequence are not analysed.

Publication References: This field contains the literature references of particular entry in coded form. The code has surname name of first or corresponding author's, last two digits of Date of publication and a identifying character in last (if required). Each reference includes title of paper, authors, year of publication and name of journal. The references are further linked to records of PUBMED database at NCBI, which provides more comprehensive information.

Source of Information:This field provide information about the source from which the all information about particular entry of database has been obtained.The information source can be public database or published literature.

Comment:This contains special information or comment about the entry . This field mostly contain the IC50 and reference IC50 values mentioned in paper to discriminate high, moderate, low and non MHC binders from each other.