Anti-pMHC & pHLA Antibody Discovery

Peptide–MHC complexes present several compounding challenges:

1. The epitope of interest is a short peptide (8–18 amino acids) displayed within a large, evolutionarily conserved MHC scaffold
2. The immune system is naturally tolerant to self-MHC molecules, suppressing responses
3. Therapeutic applications require discriminating between pMHC complexes that differ by a single amino acid — a near-identical binding surface.

These factors combined make anti-pMHC antibody generation one of the most technically demanding challenges in antibody discovery.

As a general rule, we recommend immunization-based approaches (hybridoma, single B-cell screening) for their ability to generate high-affinity antibodies through natural affinity maturation. Phage display using our immune libraries is particularly powerful for pMHC because it enables simultaneous positive and negative selection, ensuring specificity from the screening step itself. AI de novo synthesis is emerging as a valuable alternative when immune tolerance is an absolute barrier. For the highest probability of success, we recommend combining at least two approaches in parallel.

Rabbit antibodies are generated from a much broader germline diversity than mice or rats, resulting in antibodies with higher affinity, better sensitivity, and superior specificity — particularly important for complex, poorly immunogenic antigens like pMHC. The rabbit VH gene family also tends to generate epitope coverage across regions that murine antibodies often miss. For projects where the first few attempts are the most critical, rabbit immunization significantly increases the probability of success.

Immunizing with the full pMHC complex exposes the animal to the peptide in its native, MHC-bound conformation — which is the relevant structure a T cell receptor would recognize. This maximizes the chance of selecting antibodies that work in physiological and therapeutic contexts. Using a synthetic peptide alone is cost-effective and simpler, but the peptide may not adopt the same conformation as when MHC-bound, potentially generating antibodies that don’t recognize the complex on cell surfaces. We recommend running both strategies in parallel to combine the conformational fidelity of the pMHC approach with the accessibility of the peptide approach.

Specificity is built into every step of our workflow. After initial selection/screening against the target pMHC, all candidates are counter-screened against a control pMHC (same MHC molecule loaded with an irrelevant or self-peptide). Only clones that show strong binding to target pMHC and negative/background binding to control pMHC are advanced. A secondary re-screening of the best candidates is performed to confirm the specificity profile before delivery.

Yes. ProteoGenix offers a complete end-to-end service that includes recombinant pMHC antigen production as the first step. We can produce pMHC in either E. coli (with refolding) or mammalian cells (soluble secretion), depending on the HLA allele, peptide of interest, and downstream application. Our experts will guide you through the optimal production strategy during the initial project consultation.