Methods and materials for assessing response to plasmablast- and plasma cell-depleting therapies

A method for assaying CD38-expressing cells in whole blood, the method comprising:

• a) obtaining a sample of whole blood from a subject with an autoimmune disease, wherein the sample includes red blood cells, white blood cells and an anticoagulant;
• b) lysing the red blood cells to form a treated sample;
• c) freezing the treated sample to form a frozen sample, wherein freezing occurs within about 24 hours of obtaining the sample of whole blood from the subject;
• d) measuring the level of CD38-expressing cells in the sample relative to a control subject without the autoimmune disease by flow cytometry within about 72 hours of obtaining the sample, wherein the frozen sample is warmed to room temperature before measuring the level of CD38-expressing cells, wherein the CD38-expressing cells are stained with an anti-CD38 antibody conjugated to a fluorochrome, and wherein the anti-CD38 antibody comprises:
• 1) a heavy chain variable region comprising:
• i) a first CDR comprising SEQ ID NO:
• 3;
• ii) a second CDR comprising SEQ ID NO:
• 4;
• and
• iii) a third CDR comprising SEQ ID NO:
• 5;
• and
• 2) a light chain variable region comprising:
• i) a first CDR comprising SEQ ID NO:
• 6;
• ii) a second CDR comprising SEQ ID NO:
• 7;
• and
• iii) a third CDR comprising SEQ ID NO:
• 8;
• or
• 1) a heavy chain variable region comprising:
• i) a first CDR comprising SEQ ID NO:
• 13;
• ii) a second CDR comprising SEQ ID NO:
• 14;
• and
• iii) a third CDR comprising SEQ ID NO:
• 15;
• and
• 2) a light chain variable region comprising:
• i) a first CDR comprising SEQ ID NO:
• 16;
• ii) a second CDR comprising SEQ ID NO:
• 17;
• and
• iii) a third CDR comprising SEQ ID NO:
• 18;
• e) measuring the level of CD38-expressing cells relative to the control subject by assaying for free Ig light chains;
• and
• f) measuring the expression of a biomarker for an elevated expression level of at least one CD38-expressing cell-enriched gene relative to the control subject, wherein the biomarker comprises mRNA and the at least one CD38-expressing cell-enriched gene comprises CD38.