Inclusion Criteria:

- Patient (Recipient of NK Cells) Inclusion Criteria

- Relapsed patients must have high risk disease as defined by GEP risk score of ≥ 0.66
or metaphase cytogenetic abnormalities or LDH ≥ 360 U/L (Rule out hemolysis,
infection and contact PI for clarification if any doubt) Patients must have had at
least 1 line of prior chemotherapy and/or have relapsed after auto- PBSCT.

- For subjects who have had a prior transplant, ≥2 months must have relapsed after the
last transplant prior to enrollment.

- Zubrod ≤ 2, unless solely due to symptoms of MM-related (bone) disease.

- Patients must have a platelet count of ≥ 50,000/µL within 35 days of registration,
unless lower levels are explained by extensive bone marrow plasmacytosis or extensive
prior therapy.

- Patients must be at least 18 years of age and not older than 75 years of age at the
time of registration.

- Participants must have preserved renal function as defined by a serum creatinine
level of ≤ 3 mg/dL within 35 days of registration.

- Participants must have an ejection fraction by ECHO or MUGA scan ≥ 40% within 90 days
prior to registration.

- Patients must have adequate pulmonary function studies > 50% of predicted on
mechanical aspects (FEV1, FVC, etc) and diffusion capacity (DLCO) > 50% of predicted
within 90 days prior to registration. If the patient is unable to complete pulmonary
function tests due to MM related pain or condition, exception may be granted if the
principal investigator documents that the patient is a candidate for high dose
therapy.

- Patients must have signed an IRB-approved informed consent and HIPAA authorization
form.

- Either a haploidentical family donor fit to undergo leukapheresis is available or the
recipient is fit to undergo leukapheresis for exp-NK cell generation (see donor
selection).

- Patient (Recipient of NK Cells) Exclusion criteria

- History of poorly controlled hypertension, diabetes mellitus, or any other serious
medical illness or psychiatric illness that could potentially interfere with the
completion of treatment according to this protocol or could be considered to be an
exclusion criterion deemed by the PI.

- Patients must not have prior malignancy, except for adequately treated basal cell or
squamous cell skin cancer, in situ cervical cancer, or other cancer for which the
patient has not received treatment for one year prior to enrollment. Other cancers
will only be acceptable if the patient's life expectancy exceeds three years as
determined by the PI.

- Pregnant or nursing women may not participate. Women of childbearing potential must
have a negative pregnancy documented within one week of registration. Women/men of
reproductive potential may not participate unless they have agreed to use an
effective contraceptive method.

- Donor Inclusion Criteria

- The source of the NK cells will be either A) a family member who is HLA
haploidentical to the recipient, or B) if a suitable haploidentical donor is not
available, the recipient may be the source of the NK cells.

- HLA typing will be performed by the Arkansas Children's Hospital clinical laboratory.

- If the recipient expresses HLA-C group I, HLA-C group II, and Bw4 KIR ligands, then a
KIR-ligand mismatched haploidentical donor cannot be found, and the recipient will be
the source of the NK cells.

- If the recipient fails to express one or more of the primary KIR ligands (HLA-C group
I, HLA-C group II, and Bw4) then family member donors will be HLA typed in an effort
to find a haploidentical donor. If multiple haploidentical donors are available, KIR
phenotyping will be performed in Dr. van Rhee's research laboratory to select a KIR
mismatched donor whenever possible.

- Donor selection will be performed by the PI or one of the MD co-investigators if Dr.
van Rhee is not available.

- Signed IRB approved consent and HIPAA authorization form.

- Donor is not HIV I/II (+).

- Donor is not HTLV-I/II (+).

- Donor is not Hepatitis B or C (+) unless positive due to previous vaccination or has
received therapy and is negative for Hepatitis B or C by RT-PCR.

- Donor is a suitable candidate for insertion of apheresis catheter. Donors with
unusual anatomy or vascular anomalies preventing insertion of a pheresis catheter
will be rejected.

- Age 18 years or greater or has signed an Assent and be age ≥16 years.

- Donor has a negative pregnancy test by serum or urine test.

- In preparation for the peripheral blood mononuclear cell donation, the donor will
undergo a detailed medical history and physical examination. Clinical studies will
include blood chemistries (electrolytes, liver function and CRP) CBC with
differential and platelets, PT/PTT, viral panel, EKG (age over 40 yrs), and chest
x-ray (age over 40yrs). Fitness to donate cells for NK expansion will be evaluated by
a physician not involved in the initial assessment of the exp-NK cell recipient for
enrollment onto the protocol.

- Serologic evaluation will be used to assess exposure to syphilis, West Nile Virus,
Chagas, CMV IgG, hepatitis B, and C, HIV I and II, and HTLV I/II. An HIV-I/II[+] and
HTLV-1/II (+) donor will be rejected on medical grounds. Donors who been vaccinated
against hepatitis B and who have antibodies against hepatitis B surface antigen are
allowed.

- Haplo-identical donor must not have prior malignancy, except for adequately treated
basal cell or squamous cell skin cancer, in situ cervical cancer, or other cancer for
which the patient has not received treatment for one year prior to donation.

Exclusion Criteria:

- Patient (Recipient of NK Cells) Exclusion criteria

- History of poorly controlled hypertension, diabetes mellitus, or any other serious
medical illness or psychiatric illness that could potentially interfere with the
completion of treatment according to this protocol or could be considered to be an
exclusion criterion deemed by the PI.

- Patients must not have prior malignancy, except for adequately treated basal cell or
squamous cell skin cancer, in situ cervical cancer, or other cancer for which the
patient has not received treatment for one year prior to enrollment. Other cancers
will only be acceptable if the patient's life expectancy exceeds three years as
determined by the PI.

- Pregnant or nursing women may not participate. Women of childbearing potential must
have a negative pregnancy documented within one week of registration. Women/men of
reproductive potential may not participate unless they have agreed to use an
effective contraceptive method.