Company: ADPT
Filing Date: 2025-03-03
Form Type: 10-K
Source: 0000950170-25-030913
Chunk: 10

Company: Adaptive Biotechnologies Corp
Filing Date: 2025-03-03
Form: 10-K
Item: Item 1
Chunk 10
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As and neoantigens are recognized by the immune system as foreign. For autoimmune disorders, the immune system loses the ability to distinguish between ‘self’ and ‘non-self’ and mistakenly recognizes normal protein fragments (“self-antigens”) as foreign, which results in attacking otherwise healthy tissue. 

The Adaptive Immune Response 

The key cells of the adaptive immune system that enable our bodies to mount responses against antigens are called T cells and B cells. T cells can destroy target cells directly, and B cells secrete antibodies, activating other parts of the immune system to destroy targets. 

Each T cell and B cell has a unique Y-shaped receptor, which can recognize one or a small number of the millions of antigens to which our bodies are continuously exposed. When an adaptive immune response is initiated against a particular disease, the T cells and B cells encoding the disease-specific targeting receptors rapidly multiply through clonal expansion, allowing for a powerful immune response. Some of these expanded cells directly attack the disease, and others form long-term memory to allow rapid recognition of the same antigens in the future and protect against reinfection. 

Unlike all other genes in the human genome, the genetic sequences of TCRs and BCRs rearrange over time through a complex biological process resulting in massive diversity. The diversity of these receptors is made possible by a unique reshuffling of their genetic code known as V(D)J recombination (V=Variable, D=Diversity, J=Joining). This recombination process only occurs in T cells and B cells, and it results in each cell clone having a unique receptor-associated deoxyribonucleic acid (“DNA”) sequence. This unique DNA sequence acts like a barcode that can be used to identify and track an individual receptor over time, as shown in the figure below:

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The adaptive immune response requires millions of these unique receptors to be widely distributed and present in the blood in order to have the ability to rapidly respond to many different diseases simultaneously. Even after a specific TCR binds to an antigen and clonally expands, the frequency of these expanded T-cell clones containing the TCR remains relatively low in relation to the estimated trillions of other T cells that are circulating. We now know that disease-specific TCRs that are clonally expanded in a patient’s blood are present, on average, at less than 1 cell out of 100,000 cells. Despite their relatively low abundance, disease-specific TCRs can mount a systemic, persistent response to most perturbations