Common Antigen May Drive Lymphoma Proliferation

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[similarity in some CLL somatic mutations suggest a similar

situation may exist in at least some CLL patients.]

[2408] Evidence for Non-Random Immunoglobulin VH Gene and Light

Chain Isotype Usage in Follicular Non-Hodgkins Lymphoma. Session

Type: Poster Session, Board #586-II

B. Yohn, P. Van Beveren, Xi Y. Mu, Shier,

Gregg J. Silverman, P. Gold Bioinformatics, Favrille, Inc,

San Diego, CA, USA; University of California, San Diego, San Diego,

CA, USA

Background: Antibody diversity is generated by recombination of

individual immunoglobulin (Ig) gene segments and subsequent somatic

diversification driven by antigen recognition. In the repertoire of

expressed B cell receptors (BCR) among normal peripheral B cells,

variable heavy (VH) gene segments are not equally represented. The

ratio of kappa to lambda light chain usage is also skewed; the

normal / is 1.5. Investigation of the BCR repertoire may provide

clues to the genesis of B cell malignancies, as suggested in chronic

lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL). BCR V

gene identification during the production of recombinant antibodies

used in our ongoing PhII and PhIII FavId (idiotype/KLH)

immunotherapy studies has enabled us to analyze V gene usage from

475 B cell follicular lymphoma (FL) tissue samples. This study

reports the results of VH gene and / gene expression in this FL

sample collection.

Methods: Ig heavy chain (HC) and light chain (LC) isotypes from B

cell FL samples were identified by flow cytometry. VH and VL regions

were sequenced from gene specific cDNA libraries prepared from these

samples. VH gene usage and / ratios were compared to frequencies

determined for normal peripheral B cells isolated from six healthy

volunteers as well as published reports for normal peripheral B

cells and other B cell malignancies.

Results: Compared to VH gene family usage determined for normal B

cells, VH3 usage is higher (68% vs. 42%), VH1 usage is lower (7.8%

vs. 22%) and VH4 usage is equivalent (22% vs. 26%) in our cohort of

FL patients while VH2, 5, 6 and 7 are infrequently used in both

populations. Usage of the VH3 genes within FL derived sequences also

depends upon isotype, in that this gene family is preferentially

associated with the IgM HC isotype relative to IgG (76% and 57%

respectively). Additionally, the combined usage of the specific

genes VH3-23 and VH3-48 in our patient collection accounts for over

29% of all VH genes compared to 9% among normal B cells. These VH

gene usages also differ from reports of VH gene expression among CLL

and MCL patients. With respect to LC usage, VH3 isolates are

associated with a normal / ratio of 1.6 while VH4 gene isolates are

preferentially associated with light chains with a / ratio of 0.9.

Finally, FL B cells expressing the IgM HC isotype preferentially co-

express light chains (/ ratio of 2.4) while IgG expressing cells

preferentially utilize chains (/ ratio of 0.6).

Conclusions: Non-random V gene and LC expression among patients with

FL is noted. These distortions in Ig gene expression suggest that

lymphomagenesis in FL may be associated with B cell stimulation by

common antigens. A program to investigate the epitopes recognized by

FL derived BCRs via binding of recombinant FL derived antibodies to

protein arrays containing common auto-antigens is currently underway.